agar and Staphylococcal-Infections

To compare the accuracy of Mueller-Hinton agar and Isosensitest agar using cefoxitin disc for detecting methicillin resistant Staphylococcus aureus using mecA gene PCR assay as gold standard.. Comparative study.. Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, from May 2006 to January 2007.. One hundred clinical isolates of Staphylococcus aureus were evaluated; 64 MRSA (methicillin resistant Staphylococcus aureus) and 36 MSSA (methicillin sensitive Staphylococcus aureus) by mecA PCR assay. All the isolates were tested with cefoxitin 30 microg disc using semi-confluent growth on Mueller-Hinton agar as well as on Iso-sensitest agar in ambient air at 35-37 degrees C after an overnight incubation as per recommendations of Clinical and Laboratory Standard Institute.. Following diameters provided the best sensitivity and specificity without substantial overlapping between the zones of resistant and sensitive isolates; Mueller-Hinton agar: R < or = 20 mm (sensitivity 100% and specificity 100%), S > or = 22 mm (sensitivity 97.2% and specificity 100%), and Iso-sensitest agar: R < or = 26 mm (sensitivity 100% and specificity 100%), S > or = 26 mm (sensitivity 100% and specificity 100%). High accuracy was obtained with cefoxitin disc on both media.. Performance of both media was equally convincing for reliable prediction of methicillin resistance in Staphylococcus aureus by placing cefoxitin 30 microg disc on either of these in routine susceptibility testing.

Topics: Agar; Culture Media; Female; Humans; Male; Methicillin Resistance; Microbial Sensitivity Tests; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

We investigated bacterial propagation through multifilament, monofilament sutures and whether sutures coated with triclosan would exhibit a different phenomenon.. One centimetre (cm) wide trenches were cut in the middle of Columbia blood Agar plates. We tested a 6 cm length of two Triclosan-coated (PDS plus®, Vicryl plus®) and two uncoated (PDS ®, Vicryl ®) sutures. Each suture was inoculated with a bacterial suspension containing methicillin-sensitive Staphylococcus aureus (MSSA), Escherichia coli (E. coli), Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus (MRSA) at one end of each suture. The plates were incubated at 36C for 48 h, followed by room temperature for a further 5 days. We established bacterial propagation by observing for any bacterial growth on the Agar on the opposite side of the trench.. Bacterial propagation was observed on the opposite side of the trench with both suture types, monofilament PDS and multifilament Vicryl, when tested with the motile bacterium (E. coli). Propagation was not observed on the other side of the trench with the monofilament PDS suture following incubation with MSSA and S. epidermidis, and in 66% of MRSA. With multifilament suture Vicryl, propagation was observed on the other side of the trench in 90% (MSSA), 80% (S. epidermidis), and 100% (MRSA) of plates tested. No bacterial propagation was observed in any of the triclosan-coated sutures (monofilament or multifilament).. Monofilament sutures are associated in vitro with less bacterial propagation along their course when compared to multifilament sutures. Inhibition in both sutures can be further enhanced with a triclosan coating.

Topics: Agar; Anti-Infective Agents, Local; Escherichia coli; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Polyglactin 910; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus epidermidis; Surgical Wound Infection; Sutures; Triclosan

In blood cultures that test positive for staphylococcal bacteria, rapid identification of methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-susceptible Staphylococcus aureus (MSSA) by molecular assay is useful for appropriate antimicrobial treatment of bloodstream infections. Although the Xpert MRSA/SA BC assay is widely available in clinical settings in Japan, its efficacy has not yet evaluated thoroughly.. We retrospectively studied 100 blood culture cases positive for S. aureus at Sapporo Medical University Hospital between March 2019 and May 2022. Cycle threshold (CT) values for target genes from the Xpert MRSA/SA BC assay were compared to phenotypic results. Genotyping and genetic analysis of the orfX-SCCmec junction region was performed for selected isolates.. We analyzed 25 and 75 isolates assigned to MRSA and MSSA, respectively, using the Xpert MRSA/SA BC assay. Of these, 99 isolates from agar cultures showed compatible susceptibility to oxacillin. One genetically misidentified case of MRSA was found to be caused by the mixed growth of MSSA and methicillin-resistant S. hominis on agar culture. Of the 73 MSSA with pure growth on agar culture, 45 (61.6%) were found to be orfX-SCCmec-positive, spa-positive, and mecA-negative in this assay. These MSSA belong to diverse spa and coa types.. The Xpert MRSA/SA BC assay accurately identified MRSA and MSSA in positive blood cultures. However, over half of the MSSA isolates showed positive results for orfX-SCCmec, presumably due to genetic diversity in the orfX-associated region of MSSA. Therefore, the coexistence of MSSA and mecA-harboring coagulase-negative staphylococci may cause confusion about identification of MRSA.

Topics: Agar; Anti-Bacterial Agents; Blood Culture; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Pathology, Molecular; Retrospective Studies; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Fingernails are a perfect area for harboring bacteria such as Staphylococcus aureus, Salmonella sp., Shigella sp., and Escherichia coli. These bacteria under the long nails may cause diseases due to the contact of nails with food or while biting the nails. Our study aimed to compare the antibacterial activity of chloroxylenol and thymol, two different detergent ingredients, on microorganisms isolated from long fingernails. This study was performed to raise awareness of the dangers of long nails and the importance of good nail hygiene.. The present study was performed on female students at the Faculty of Science, King Abdelaziz University. Bacteria were isolated from under one finger nails and cultured on both McConkey agar and mannitol salt agar. After incubation, we isolated bacteria on nutrient agar. After that, we conducted several tests to determine the isolate type. Finally, we prepared three different concentrations of chloroxylenol and thymol to compare their effect on the isolated bacteria using antibacterial activity on Mueller-Hinton agar.. Two types of bacteria were isolated, pathogenic bacteria called Staphylococcus aureus and non-pathogenic bacteria called Staphylococcus epidermidis. Staphylococci have more sensitivity to chloroxylenol than thymol. In addition, chloroxylenol, at high concentrations had a more powerful antibacterial effect.. The results emphasized that fingernails could harbor pathogenic bacteria which are difficult to remove. Perfect hand hygiene is essential to prevent the spread of diseases.

Topics: Agar; Anti-Bacterial Agents; Bacteria; Culture Media; Escherichia coli; Female; Humans; Microbial Sensitivity Tests; Nails; Staphylococcal Infections; Staphylococcus aureus; Thymol

Topics: Agar; Animals; Anti-Bacterial Agents; Coinfection; Cystic Fibrosis; Phenotype; Sheep; Staphylococcal Infections; Staphylococcus aureus

Respiratory tract infections cause significant morbidity and mortality globally and are the most common infectious diseases in humans. This study aims at assessing the presence of bacterial respiratory infections, number of people infected and antimicrobial susceptibility profile among antibiotic naïve outpatients presenting with respiratory tract infections in Meru Teaching and Referral Hospital.. The study was conducted in Meru Teaching and Referral Hospital, Meru County from April 2017 to August 2018. Upper respiratory infections were characterized by acute infection of nasal cavity, pharynx and larynx while lower respiratory infections were characterized by chest pains, prolonged cough, productive sputum, difficulty in breathing, fever and weight loss. A total of 384 sputum and throat samples were collected aseptically from patients who were clinically suspected to have respiratory infections and cultured in blood agar, MacConkey agar and chocolate agar. Bacterial isolates were identified by colonial morphology, Gram stain and confirmed by biochemical tests. Antimicrobial susceptibility profile was determined using agar disc diffusion method.. Respiratory bacterial pathogens were isolated in 45.6% of the samples. The prevalence of the bacteria species isolated were as follows Pseudomonas species (36.6%), Klebsiella species (20.6%), Staphylococcus aureus (16.6%), Streptococcus pyogenes (13.7%), Streptococcus pneumoniae (10.3%) and mixed isolates (2.3%). Amoxicillin and ampicillin recorded the highest resistance rate. Most of the isolates displayed high level of resistance to more than two antibiotics. Although multidrug resistance is reported in the study, gentamicin, amikacin and cefuroxime are recommended as the antibiotics of choice against bacterial isolates obtained.. Bacterial respiratory infections were prevalent in the study area and the isolates obtained showed resistance to commonly used antibiotics such as amoxicillin, ampicillin, ciprofloxacin piperacillin ciprofloxacin, ceftazidime, piperacillin-tazobactam and cephalexin. Therefore need for a continuous surveillance of antimicrobial resistance in management of respiratory infections in the study area.

Topics: Agar; Amoxicillin; Ampicillin; Anti-Bacterial Agents; Ciprofloxacin; Humans; Kenya; Outpatients; Piperacillin; Respiratory Tract Infections; Staphylococcal Infections

The aim of this study was the development of a methodology for the integral study of the antagonistic activity of normal human microbiota against Staphylococcus aureus to enable direct selection (without prior isolation of pure cultures) of potentially highly efficient probiotic preparations. The selection of bacterial representatives of normal human nasal microbiota capable of antagonizing S. aureus was carried out using two complimentary methods: replica-plating and deferred antagonism procedures. The material of the anterior nares from healthy human subjects was plated onto the surface of different nutrient media agar plates followed by incubation under appropriate conditions. The grown bacterial colonies were replica-plated to Petri dishes with nutrient agar overlayed with a thin layer of a soft agar which contained the culture of an indicator S. aureus strain. This agar also supported the growth of potential probiotic strains. The potential probiotic strains were selected by their ability to suppress the growth of S. aureus around their colonies. Most active strains-inhibitors may be used to develop probiotic preparations with targeted activity against S. aureus.

Topics: Agar; Culture Media; Humans; Probiotics; Staphylococcal Infections; Staphylococcus aureus

Staphylococcus aureus is a unique challenge for the healthcare system because it can form biofilms, is resistant to the host's immune system, and is resistant to numerous antimicrobial therapies. The aim of this study was to investigate the effect of poly (lactic-co-glycolic acid) (PLGA) polymer nanoparticles loaded with vancomycin and conjugated with lysostaphin (PLGA-VAN-LYS) on inhibiting S. aureus biofilm formation. Nano drug carriers were produced using the double emulsion evaporation process. we examined the physicochemical characteristics of the nanoparticles, including particle size, polydispersity index (PDI), zeta potential, drug loading (DL), entrapment efficiency (EE), Lysostaphin conjugation efficiency (LCE), and shape. The effect of the nano drug carriers on S. aureus strains was evaluated by determining the minimum inhibitory concentration (MIC), conducting biofilm formation inhibition studies, and performing agar well diffusion tests. The average size, PDI, zeta potential, DL, EE, and LCE of PLGA-VAN-LYS were 320.5 ± 35 nm, 0.270 ± 0.012, -19.5 ± 1.3 mV, 16.75 ± 2.5%, 94.62 ± 2.6%, and 37% respectively. Both the agar well diffusion and MIC tests did not show a distinction between vancomycin and the nano drug carriers after 72 h. However, the results of the biofilm analysis demonstrated that the nano drug carrier had a stronger inhibitory effect on biofilm formation compared to the free drug. The use of this technology for treating hospital infections caused by the Staphylococcus bacteria may have favorable effects on staphylococcal infections, considering the efficacy of the nano medicine carrier developed in this study.

Topics: Agar; Biofilms; Glycols; Humans; Lysostaphin; Polymers; Staphylococcal Infections; Staphylococcus aureus; Vancomycin

From 1 January to 31 December 2022, fifty-five institutions across Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP). The aim of ASSOP 2022 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 3,214 SAB episodes were reported, of which 77.5% were community-onset. Overall, 15.0% of S. aureus were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 21.4%, which was significantly different to the 16.8% all-cause mortality associated with methicillin-susceptible SAB (p = 0.02). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 31% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 13% to tetracycline; 11% to gentamicin; and 2% to co-trimoxazole. One MRSA isolate, with a daptomycin MIC of 1.5 mg/L, harboured the A302V mprF and A23V cls2 mutations. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in one MRSA isolate. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and to the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired resistance to multiple antimicrobials including ciprofloxacin, clindamycin, erythromycin, gentamicin, and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 86% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 72% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST97-IV [2B]; ST953-IV [2B]; and ST8-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

Topics: Agar; Anti-Bacterial Agents; Anti-Infective Agents; Australia; Bacteremia; Ciprofloxacin; Cross Infection; Drug Resistance, Bacterial; Erythromycin; Gentamicins; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Staphylococcal Infections; Staphylococcus aureus; Tetracycline

Difficult-to-treat infections caused by antibiotic-susceptible strains have been linked to the occurrence of persisters, a subpopulation of dormant bacteria that tolerate antibiotic exposure despite lacking genetic resistance. These persisters can be identified phenotypically by plating on nutrient agar because of their altered growth dynamics, resulting in colony-size heterogeneity. The occurrence of within-patient bacterial phenotypic heterogeneity in various infections and clinical determinants of persister formation remains unknown.. We plated bacteria derived from 132 patient samples of difficult-to-treat infections directly on nutrient-rich agar and monitored colony growth by time-lapse imaging. We retained 36 Staphylococcus aureus monocultures for further analysis. We investigated clinical factors associated with increased colony growth-delay with regression analyses. We corroborated the clinical findings using in vitro grown static biofilms exposed to distinct antibiotics.. The extent of phenotypic heterogeneity of patient-derived S. aureus varied substantially between patients (from no delay to a maximum of 57.6 hours). Increased heterogeneity coincided with increased median colony growth-delay. Multivariable regression showed that rifampicin treatment was significantly associated with increased median growth-delay (13.3 hours; 95% CI 7.13-19.6 hours; p < 0.001). S. aureus grown in biofilms and exposed to high concentrations of rifampicin or a combination of rifampicin with clindamycin or levofloxacin exhibited prolonged growth-delay (p < 0.05 for 11 of 12 comparisons), correlating with a strain-dependent increase in antibiotic tolerance.. Colony-size heterogeneity upon direct sampling of difficult-to-treat S. aureus infections was frequently observed. Hence, future studies are needed to assess the potential benefit of phenotypic heterogeneity quantification for staphylococcal infection prognosis and treatment guidelines.

Topics: Agar; Anti-Bacterial Agents; Biofilms; Humans; Microbial Sensitivity Tests; Rifampin; Staphylococcal Infections; Staphylococcus aureus

Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) is routinely used for bacterial identification in clinical laboratories. Bacterial protein expression may differ according to their growth conditions, especially the culture medium composition. We aimed to study the peak variations of Staphylococcus aureus grown on various blood agar plates (BAP), especially phenol-soluble modulin-mec (PSM-mec) peak (m/z 2409) associated with mecA gene conferring methicillin resistance. Methicillin-resistant S. aureus (MRSA) ATCC 43300 and eight clinical MRSA isolates were cultured on various commercial BAPs including tryptic soy agar-based BAPs, Columbia agar-based BAP and in-house BAPs with the addition of yeast extract. Analysis of the MALDI-TOF peaks of S. aureus, cultured on various BAPs, revealed the peak intensities of low-molecular weight proteins to vary depending on the composition of BAPs, especially the presence or absence of yeast extract. Especially, the PSM-mec and delta-toxin peaks showed low intensity for S. aureus ATCC 43300 and clinical isolates. No significant differences were found in the number of peaks, but some peaks had lower intensity, corresponding to the medium containing yeast extract, in low-mass region (< m/z 4000). BAPs based on tryptic soy agar rather than Columbia agar seems to be appropriate for the detection of PSM-mec, a methicillin resistance marker of S. aureus and delta-toxin, an agr function indicator.

Topics: Agar; Humans; Lasers; Methicillin-Resistant Staphylococcus aureus; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Staphylococcal Infections; Staphylococcus aureus

From 1 January to 31 December 2020, forty-nine institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aims of ASSOP 2020 were to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin; and to characterise the molecular epidemiology of the methicillin-resistant isolates. A total of 2,734 SAB episodes were reported, of which 79.7% were community-onset. Of S. aureus isolates, 17.6% were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 14.2%, which was not significantly different from the 13.3% mortality associated with methicillin-susceptible SAB (p = 0.6). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 35% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin, 33% to ciprofloxacin, 13% to tetracycline, 13% to gentamicin and 4% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in four S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA (HA-MRSA) clones: ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. However, 85% percent of methicillin-resistant SAB isolates were community-associated MRSA (CA-MRSA) clones. Although polyclonal, approximately 77% of CA-MRSA clones were characterised as: ST93-IV [2B] (Queensland CA-MRSA); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST8-IV [2B]; and ST97-IV [2B]. The CA-MRSA clones, in particular ST45-V [5C2&5], have acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The multi-resistant ST45-V [5C2&5] clone accounted for 11.0% of CA-MRSA. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus sepsis.

Topics: Agar; Anti-Bacterial Agents; Anti-Infective Agents; Australia; Bacteremia; Ciprofloxacin; Cross Infection; Drug Resistance, Bacterial; Erythromycin; Gentamicins; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Sepsis; Staphylococcal Infections; Staphylococcus aureus; Tetracyclines

mobile phone plays an essential role in the lives of healthcare professionals in hospitals as far as communication is concerned. However, it can also serve as a source of nosocomial infections. This study aimed at determining the prevalence and antibiotic susceptibility of Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli isolated from mobile phones used by healthcare staff working in three public hospitals in Ghana.. in total, 220 swab samples were collected from 110 mobile phones of healthcare workers at a referral and two public tertiary hospitals in Ghana. Direct spreading of swab samples on agar plates was done. MacConkey agar and Baird Parker agar were used to isolate E. coli and S. aureus, respectively. Clinical Laboratory Standard Institute´s guidelines were followed for susceptibility testing, and S. aureus strains resistant to cefoxitin were considered to be MRSA. All E. coli and MRSA isolates were tested for their susceptibility to antibiotics using European Committee on Antimicrobial Susceptibility Testing (EUCAST) 2018 guidelines with its breakpoints. Obtained qualitative data were analyzed by using Microsoft Excel.. of 110 mobile phones, 78 (70.9%) and 4 (3.6%) were colonized with S. aureus and E. coli, respectively. From the 78 S. aureus isolates, 22 (28%) isolates were MRSA. Fifty percent (50%) (11/22) of the MRSA isolates were multi-drug resistant, of which one isolate was resistant to all antibiotics tested. E. coli isolates had 100 resistances to both ceftriaxone and ceftazidime.. mobile phones used by healthcare workers in hospitals frequently harbor E. coli, S. aureus, MRSA and may be sources of hospital-associated infections.

Topics: Agar; Anti-Bacterial Agents; Cell Phone; Cross Infection; Drug Resistance, Microbial; Escherichia coli; Escherichia coli Infections; Ghana; Health Personnel; Hospitals, Public; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Staphylococcal Infections; Staphylococcus aureus

Calcium sulfate bone void filler beads are fully absorbable in the body, and are often used in complicated orthopedic infection cases to release a relatively high dose of antibiotics locally to the body site over time. However, the antibiotic resistance crisis and/or inability to treat chronic biofilm infections remains to be a formidable and increasing health threat. In this report, we tested the hypothesis that plant essential oils (PEOs) with anti-staphylococcal qualities could inhibit the growth of Staphylococcus aureus (a major etiological agent of periprosthetic joint infection) in agar pour plates when infused in calcium sulfate beads. To begin, we conducted a screen of 57 single plant PEOs for anti-staphylococcal activity via disk diffusions assays. We observed that 55/57 of the PEOs had significant growth inhibitory activity compared to the null hypothesis, and 41/57 PEOs exhibited activity similar-to-or-higher-than a vancomycin minimum inhibitory control. When PEOs were infused in beads, we observed that 17/57 PEOs tested exhibited significant bacterial growth inhibition when encased in S. aureus-seeded agar compared to a null hypothesis of six millimeters (bead size). However, none of the PEO-beads had activity similar to a vancomycin bead control made according to a clinically relevant formula. To the best of our knowledge, this is the first report and screen of PEOs for growth inhibitory activity when infused in lab-made calcium sulfate beads. These data indicate that antibacterial PEOs warrant further investigations, and may be useful in developing new treatment strategies for periprosthetic joint infection.

Topics: Agar; Anti-Bacterial Agents; Arthritis, Infectious; Calcium Sulfate; Emulsions; Humans; Microbial Sensitivity Tests; Oils, Volatile; Prosthesis-Related Infections; Staphylococcal Infections; Staphylococcus aureus; Vancomycin; Water

Fosfomycin resistance has become a clinical concern. In this study, we analysed the dynamic change of fosfomycin MIC in the epidemic Staphylococcus aureus lineages in a teaching hospital in Shanghai for 12 years and sought to elucidate the major underlying mechanisms.. MLST was conducted for 4580 S. aureus isolates recovered from 2008 to 2019. Fosfomycin MIC was determined by the agar dilution method. The genome data of 230 S. aureus epidemic lineage isolates were acquired from a next-generation sequencing (NGS) platform. Gene deletion and corresponding complementation mutants were constructed to confirm the mechanism of fosfomycin resistance.. The predominant S. aureus lineages during the past 12 years were ST5 and ST239 (45.6%; 2090/4580). However, ST5 has been spreading clinically, while ST239 has gradually disappeared recently. Consistent with epidemic trends, fosfomycin-resistant ST5 increased from 19.5% to 67.3%. Most fosfomycin-resistant ST5 isolates (92.7%; 647/698) possessed high-level resistance (MIC > 1024 mg/L) with combined mutations mainly in glpT and uhpT. In contrast, fosfomycin-resistant ST239 isolates (76.8%; 149/194) mainly acquired low-level resistance (MIC = 64-128 mg/L) with mutation primarily in hptA. Deletion of a single resistant gene merely resulted in low-level fosfomycin resistance, while double-gene mutants ΔglpTΔuhpT, ΔglpTΔhptA and ΔglpTΔhptR acquired high-level fosfomycin resistance.. The high-level fosfomycin resistance of S. aureus epidemic lineage ST5 is mainly due to the accumulation of mutations in the resistant genes related to membrane transporter systems, and partly contributes to its persistent prevalence under clinical antibiotic pressure.

Topics: Agar; Anti-Bacterial Agents; China; Fosfomycin; Humans; Membrane Transport Proteins; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Multilocus Sequence Typing; Staphylococcal Infections; Staphylococcus aureus

To determine the frequency and antibiotic susceptibility pattern of CA-MRSA in patients with uncomplicated skin and soft tissue infections reporting to the dermatology outpatient of a tertiary health care hospital.. A descriptive study.. Dermatology outpatient of a tertiary care hospital in Punjab province of Pakistan, from September 2020 to August 2021.. Patients of all age groups and both genders reporting during the study period with community-associated uncomplicated bacterial skin and soft tissue infections were enrolled in the study. Samples were collected from skin lesions and cultured on blood agar and MacConkey agar plates. Antimicrobial susceptibility testing using the modified Kirby Baur disc diffusion technique was performed.. A total of 157 patients were included in the study. Impetigo was most common infection (n=80, 51%), followed by Furunculosis (n=47, 29.9%). The frequency of MRSA isolates was 54.1% (n=85). MRSA was significantly more frequently isolated from patients with furunculous, carbuncle and cutaneous abscesses as compared to impetigo. All MRSA isolates were sensitive to linezolid, teicoplanin, and vancomycin. 97.6%, 84.7%, and 72.9% of MRSA isolates were sensitive to rifampicin, minocycline, and fusidic acid respectively. 89.4% of MRSA were sensitive to amikacin and clindamycin. 63.5% were sensitive to doxycycline and 58.8% were sensitive to co-trimoxazole. Only 20% of MRSA were sensitive to ciprofloxacin.. The antibiotics active against CA-MRSA including rifampicin, minocycline, amikacin, and clindamycin may be used empirically in patients with furunculosis, cutaneous abscess, and carbuncles. Linezolid, teicoplanin, and vancomycin should be reserved for severe infections.. Uncomplicated skin and soft tissue infections, Community-associated Methicillin-resistant staphylococcus aureus (CA-MRSA), Antibiotic susceptibility pattern.

Topics: Agar; Amikacin; Animals; Anti-Bacterial Agents; Clindamycin; Community-Acquired Infections; Female; Furunculosis; Humans; Impetigo; Linezolid; Male; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Minocycline; Rifampin; Soft Tissue Infections; Staphylococcal Infections; Staphylococcal Skin Infections; Teicoplanin; Vancomycin

From 1 January to 31 December 2021, forty-eight institutions around Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Programme (ASSOP). The aim of ASSOP 2021 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 2,928 SAB episodes were reported, of which 78.4% were community-onset. Overall, 16.9% of S. aureus isolates were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 15.0%, which was not significantly different from the 14.4% all-cause mortality associated with methicillin-susceptible SAB (p = 0.7). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 36% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 15% to tetracycline; 16% to gentamicin; and 3% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in three S. aureus isolates. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 85% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 68% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST45-V [5C2&5]; ST5-IV [2B]; ST1-IV [2B]; ST30-IV [2B]; and ST97-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

Topics: Agar; Anti-Bacterial Agents; Anti-Infective Agents; Australia; Bacteremia; Ciprofloxacin; Cross Infection; Drug Resistance, Bacterial; Erythromycin; Gentamicins; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Staphylococcal Infections; Staphylococcus aureus; Tetracycline

Staphylococcus lugdunensis is a Gram-positive coagulase-negative bacterium and is recognized as a critical pathogenic species recently. Here, we aimed to evaluate the cefoxitin disk diffusion (CDD), oxacillin agar dilution (OAD), and mecA PCR for detecting oxacillin-resistant S. lugdunensis (ORSL) isolates.. Multilocus sequence typing (MLST) analysis was performed to determine the clonality of 117 S. lugdunensis isolates isolated between May 2009 and Jul 2014. CDD, OAD, and mecA PCR were used to identify oxacillin-resistant S. lugdunensis (ORSL).. MLST results showed that the most common sequence type (ST) of our S. lugdunensis isolates was ST6 (35.9%) followed by ST3 (28.2%), ST27 (17.9%), and ST4 (6.8%). CDD and OAD showed that 39 and 43 isolates were ORSL, respectively. 4 ST3 CDD-susceptible S. lugdunensis (OSSL) isolates had MIC values ≥ 4 for oxacillin. mecA PCR results showed that 43 OAD-resistant S. lugdunensis and 3 OAD-susceptible ST27 S. lugdunensis had the mecA gene. Therefore, OAD was used as the gold standard to evaluate the performance of CDD and mecA PCR for identifying ORSL. The overall sensitivity, specificity, and accuracy of CCD for ORSL detection was 90.7%, 100%, and 96.8%, respectively. The sensitivity, specificity, and accuracy of mecA PCR for identifying ORSL was 100%, 95.9%, and 97.44%, respectively.. Our results indicate that OAD shows higher accuracy for ORSL detection compared with CDD and mecA PCR.

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Cefoxitin; Drug Resistance, Bacterial; Humans; Microbial Sensitivity Tests; Multilocus Sequence Typing; Oxacillin; Staphylococcal Infections; Staphylococcus lugdunensis

Methicillin-resistant Staphylococcus aureus is a global public health challenge and there is a continuous increase in community-acquired infections among people in different geographical location. We sought the distribution and antibiotics pattern of community-acquired methicillin-resistant Staphylococcus isolates among apparently healthy residents of Ibadan, Southwestern Nigeria.. Seven hundred (700) healthy volunteers residing in Ibadan metropolis, Nigeria, were enrolled in this study. Isolates from the nasal swabs were aseptically collected and characterized using standard and established microbiological methods, which included growth and fermentation on mannitol salt agar, colonial morphology, Gram-staining reaction, Microbact™ 12S identification kit and confirmed with 16SrRNA. After identification of the isolates, antimicrobial susceptibility test was performed on Mueller-Hinton agar by modified Kirby-Bauer disc diffusion method and the presence of mecA and nuc genes were detected via polymerase chain reaction assay.. Prevalence of Staphylococcus aureus nasal carriage and Methicillin-resistant Staphylococcus in this study was 31.9% and 9.43% respectively. The residents of Ibadan North local government area (Fisher's Exact = 1.8962, P = .028) and Egbeda local government area (Fisher's Exact = 2.7222, P = .006) are likely to carry Methicillin-resistant Staphylococcus than any other local government area in Ibadan, Nigeria. The antimicrobial resistance patterns of the isolates revealed high resistance to Oxacillin (96.9%). Most of the isolates were sensitive to vancomycin (92.4%). Polymerase chain reaction analysis showed that mecA gene was present in all 66 (100%) Methicillin-resistant Staphylococcus aureus isolates. Male-gender (ϰ. Our findings revealed the relatively high frequency of nasal carriers of Methicillin-resistant Staphylococcus aureus among the apparently healthy residents of the studied area and the advent of multidrug resistance among these isolates. Our study also supports previous findings on male-gender and low educational background as risk factors of S. aureus carriage. The need for rational chemotherapy, routine detection and regular surveillance of Methicillin-resistant Staphylococcus to limit its spread and reduce treatment failures is important.

Topics: Adult; Agar; Anti-Bacterial Agents; Humans; Male; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Middle Aged; Nigeria; Staphylococcal Infections; Staphylococcus aureus

Dalbavancin is a novel glycopeptide antibiotic approved for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). It is characterized by a potent activity against numerous Gram-positive pathogens, a long elimination half-life and a favorable safety profile. Most recently, its application for the treatment of periprosthetic joint infections (PJIs) was introduced. The aim of this study was to proof our hypothesis, that dalbavancin shows superior efficacy against staphylococcal biofilms on polyethylene (PE) disk devices compared with vancomycin and additive behavior in combination with rifampicin. Staphylococcus aureus biofilms were formed on PE disk devices for 96 h and subsequently treated with dalbavancin, vancomycin, rifampicin and dalbavancin-rifampicin combination at different concentrations. Quantification of antibacterial activity was determined by counting colony forming units (CFU/ml) after sonification of the PE, serial dilution of the bacterial suspension and plating on agar-plates. Biofilms were additionally life/dead-stained and visualized using fluorescence microscopy. Dalbavancin presented superior anti-biofilm activity compared to vancomycin. Additive effects of the combination dalbavancin and rifampicin were registered. Dalbavancin combined with rifampicin presents promising anti-biofilm activity characteristics in vitro. Further in vivo studies are necessary to establish recommendations for the general use of dalbavancin in the treatment of PJIs.

Topics: Agar; Anti-Bacterial Agents; Biofilms; Drug Synergism; Glycopeptides; Humans; In Vitro Techniques; Microbial Sensitivity Tests; Microscopy, Fluorescence; Polyethylene; Rifampin; Staphylococcal Infections; Staphylococcus aureus; Stem Cells; Teicoplanin; Vancomycin

Staphylococcus aureus is part of the nasal microbiota in 20-30% of the population. This colonization is also a reservoir for its dissemination, which is worrying in the case of strains with resistance to methicillin (MRSA).. To determine S. aureus nasal carriage in nursing and medical students of San Felipe Campus and characterize theirs isolates.. During 2017, nasal swabs were taken from 225 students and seeded in salt manitol agar. Antibiotypes were determined by agar diffusion and the genetic clonality was assessed by PFGE and MLST in isolated S. aureus. SCCmec cassette and Panton-Valentine leukocidin gene (pvl) presence were determined in the MRSA isolates.. 61 students carried S. aureus (27.1%) including two MRSA strains (0.9%). S. aureus showed resistance to penicillin (75%), erythromycin (14%) and clindamycin (10%), chloramphenicol (1.6%) and levofloxacin, oxacillin, cefoxitin (3.3%). Nineteen PFGE-types were differentiated, and their sequence-types coincided with main clonal complexes described in S. aureus carriers from different places worldwide: CC30, CC8, CC97, CC15, CC22 and CC1. MRSA strains belonged to CC5 and they corresponded to the Chilean/Cordobes and USA100NY/J clones.. Nasal carriage of S. aureus and MRSA in students, coincided with the general population and sensitive-methicillin strains showed clonal diversity and high antimicrobial susceptibility except for penicillin.

Topics: Agar; Anti-Bacterial Agents; Chile; Genotype; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Multilocus Sequence Typing; Staphylococcal Infections; Staphylococcus aureus; Students, Nursing

This study evaluated disc diffusion tests and agar screening for detecting mecA-mediated oxacillin resistance in Staphylococcus lugdunensis (S. lugdunensis).. Staphylococcus lugdunensis isolates (n = 179) from diverse sources in Hong Kong during 1998-2018 were investigated by disc diffusion tests (cefoxitin and oxacillin) and inoculation onto oxacillin (1 μg/mL and 2 μg/mL) and chromID methicillin-resistant Staphylococcus aureus (MRSA) agars. The results were compared with mecA PCR as the reference. Isolates with discordant results were further tested by MIC and penicillin-binding protein 2a (PBP2a) assays.. Cefoxitin and oxacillin zone diameters were not distributed in ways that allowed reliable division of the mecA-positive (n = 52) and mecA-negative (n = 127) isolates. On applying the 2019 Clinical Laboratory Standards Institute (CLSI) M100 breakpoints for cefoxitin disc results, there was 88% categorical agreement (CA) and 40% very major error (VME). Screening using 2 μg/mL oxacillin agar reliably differentiated mecA-positive and mecA-negative isolates (100% CA) without any major error (ME) or VME results. The performance of screening using 1 μg/mL oxacillin agar or ChromID MRSA agar was variable (74-89% CA, 0-38% ME and 0-37% VME). The mecA-positive isolates (n = 21) that could not be detected by the cefoxitin disc test were further characterised. The cefoxitin MIC for all 21 isolates was ≤4 μg/mL. Twenty isolates had an oxacillin MIC of 1-2 μg/mL and one had an oxacillin MIC of 4 μg/mL. All had positive PBP2a results and were typed as clonal cluster 27/SCCmec V.. These findings highlight the need to evaluate phenotypic methods using mecA-positive S. lugdunensis with different oxacillin resistance phenotypes.

Topics: Agar; Bacterial Load; Bacterial Proteins; Carrier State; Cefoxitin; Disk Diffusion Antimicrobial Tests; Humans; Methicillin Resistance; Microbial Sensitivity Tests; Oxacillin; Phenotype; Staphylococcal Infections; Staphylococcus lugdunensis

Natural indicator, red cabbage extract (RCE) incorporated agars were developed, for the first time, as colorimetric sensors for identification of MRSA and MRSE. These strains were differentiated in RCE media with addition of plasma due to coagulase positive property of MRSA, they were differentiated by manipulating NaCl and introducing gelatin in RCE agar. RCE agar was examined based on concentration of NaCl and MRSA concentrations and incubation time for detection of MRSA. RCE agar was prepared mixing 10g peptone, 1g beef extract, NaCl, 15 mg/mL agar and 25% RCE in distilled water and sterilized in autoclave at 121°C for 15 min. 4 μg/mL cefoxitin was added to mixture based on experiment. The color of RCE agar including 50 mg/mL NaCl was turned to pink dependent upon growth of MRSA, MRSE and MSSA, growth of E. coli was inhibited due to its salt intolerance property. Introducing 4 μg/mL cefoxitin, growth of MRSA was not observed. 1 CFU/mL, 10 CFU/mL, 100 CFU/mL and 1000 CFU/mL of MRSA inoculated on the RCE agar showed growth and led color change in 24 hrs. Additionally, slight pink spots on RCE agar and pale pink color on whole RCE agar were appeared in 8th hrs and 11th hrs of inoculation, respectively when 1000 CFU/mL of MRSA used. The RCE agar was successfully used for detection of MRSA and differentiation of them. Finally, the RCE agar can be implemented in clinics and may alleviate incubation time and cost compared to the chromogenic agars.

Topics: Agar; Culture Media; Escherichia coli; Humans; Methicillin Resistance; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Culture Media; Humans; Japan; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Specimen Handling; Staphylococcal Infections

Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a major cause of chorioamnionitis and neonatal sepsis. This study evaluates Raman spectroscopy (RS) to identify spectral characteristics of infection and differentiate GBS from Escherichia coli and Staphylococcus aureus during ex vivo infection of human fetal membrane tissues. Unique spectral features were identified from colonies grown on agar and infected fetal membrane tissues. Multinomial logistic regression analysis accurately identified GBS infected tissues with 100.0% sensitivity and 88.9% specificity. Together, these findings support further investigation into the use of RS as an emerging microbiologic diagnostic tool and intrapartum screening test for GBS carriage.

Topics: Agar; Algorithms; Anti-Bacterial Agents; Chorioamnionitis; Escherichia coli; Escherichia coli Infections; Extraembryonic Membranes; Female; Humans; Logistic Models; Microbiological Techniques; Pregnancy; Regression Analysis; Spectrum Analysis, Raman; Staphylococcal Infections; Staphylococcus aureus; Streptococcal Infections; Streptococcus agalactiae

No single material can provide all requirements for wound dressings. Here, we evaluated the influence of different soy protein isolate and agar proportions (3:1, 1:1, and 1:3) in blend films on some of their physical-chemical and antibacterial properties to elucidate their potential as wound dressings. The films were synthesized by the gel casting method and ciprofloxacin hydrochloride was incorporated into the films. Films were characterized based on their surface morphology, water uptake ability, and weight loss profile. Also, the ciprofloxacin hydrochloride release kinetics was quantified spectrophotometrically. The antibacterial effect was evaluated against Staphylococcus aureus and Pseudomonas aeruginosa strains. The soy protein isolate-agar ratio affected the water uptake of the films and the release profile of ciprofloxacin hydrochloride but not the weight loss profile. The amount of drug released decreased near 80% because of the decrease in agar content in the films. The release kinetics of ciprofloxacin hydrochloride data best fitted to the Korsmeyer-Peppas model, suggesting that the mechanism of drug release was mainly of the diffusion type. All ciprofloxacin hydrochloride-releasing soy protein isolate-agar films strongly inhibited the cell viability of the bacterial strains studied. We concluded that water uptake and ciprofloxacin hydrochloride release can be controlled by changing the soy protein isolate-agar proportion. The proportions did not lead to changes in the antibacterial strength of the films.

Topics: Agar; Anti-Bacterial Agents; Bandages; Ciprofloxacin; Drug Carriers; Drug Delivery Systems; Drug Liberation; Humans; Pseudomonas aeruginosa; Pseudomonas Infections; Soybean Proteins; Staphylococcal Infections; Staphylococcus aureus; Wound Healing

Rapid identification of bacteria is critical in clinical and food safety applications. This paper describes a novel instrument and data analysis method for identifying bacteria based on the measurement of laser light scattering as the beam interacts with bacterial cells suspended in water. A description of the technology is followed by an identification performance study for a set of strains from the genus Staphylococcus (the inclusive target organisms) and a set of non-Staphylococcus strains (the exclusive organisms). Staphylococcus and non-Staphylococcus cells were grown on sheep blood agar (SBA), tryptic soy agar, brain heart infusion (BHI) agar, or Luria-Bertani (LB) agar and identified based on how cells scattered light. Bacteria from the genus Staphylococcus grown on solid media were correctly identified more than 92% of the time. To determine whether the system could also identify bacteria grown in liquid culture, six different Staphylococcus strains and six different non-Staphylococcus strains were grown in tryptic soy broth, BHI broth, or LB broth. This system accurately identified all targeted Staphylococcus samples tested, and no misidentifications occurred. A single-blind identification experiment was also performed on human clinical isolates obtained from the Upper Peninsula Health System. Ninety blind-coded clinical bacterial isolates on SBA were tested to determine whether they were from the genus Staphylococcus. All Staphylococcus were accurately identified, and no misidentifications occurred. This study demonstrated the proof of concept of a novel system that can rapidly and accurately identify bacteria from pure culture based on cellular light-scattering properties.

Topics: Agar; Algorithms; Bacteriological Techniques; Culture Media; Dynamic Light Scattering; Humans; Lasers; Single-Blind Method; Staphylococcal Infections; Staphylococcus

Contaminated suture material plays an important role in the physiopathology of surgical site infections. Recently, suture material has been developed characterized by barbs projecting from a monofilament base. Claimed advantages for barbed sutures are a shortened wound closure time and reduced maximum wound tension. It has also been suggested that these sutures would be advantageous microbiologically. The aim of this study was to test the microbiological characteristics of the barbed Quill in comparison to the monofilament Ethilon II and the braided sutures Vicryl and triclosan-coated Vicryl Plus. In our study, sutures were cultivated on color-change agar with Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecium, Escherichia coli, and Pseudomonas aeruginosa and the halo size was measured. In a second study arm with longer cultivation bacterial growth was followed by antibiotic treatment. Ethilon II and Quill showed good comparable results, whereas large halos were found around Vicryl. Vicryl Plus results depended on triclosan sensitivity. After longer bacterial cultivation and antibiotic treatment, halos were up to 3.6 times smaller on Quill than on Vicryl (p < 0.001), but 1.4 times larger than on Ethilon II (p < 0.001) regarding S. aureus. Confocal microscopy analysis showed bacterial colonization between the braided filaments on Vicryl and beneath the barbs on Quill. From a microbiological perspective, barbed sutures can be recommended in aseptic surgery, but should only be used carefully in septic surgery. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:925-933, 2017.

Topics: Agar; Bacterial Adhesion; Biofilms; Enterococcus faecium; Escherichia coli; Microscopy, Confocal; Polyglactin 910; Pseudomonas aeruginosa; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus epidermidis; Surgical Wound Infection; Suture Techniques; Sutures; Triclosan; Wound Healing

Platelet Concentrates (PCs) are the blood components with the highest rate of bacterial contamination, and coagulase-negative staphylococci (CoNS) are the most frequently isolated contaminants. This study investigated the biofilm formation of 16 contaminated units out of 691 PCs tested by phenotypic and genotypic methods. Adhesion in Borosilicate Tube (ABT) and Congo Red Agar (CRA) tests were used to assess the presence of biofilm. The presence of icaADC genes was assessed by means of the Polymerase Chain Reaction (PCR) technique. With Vitek(r)2, Staphylococcus haemolyticus was considered the most prevalent CoNS (31.25%). The CRA characterized 43.8% as probable biofilm producers, and for the ABT test, 37.5%. The icaADC genes were identified in seven samples by the PCR. The ABT technique showed 85.7% sensitivity and 100% specificity when compared to the reference method (PCR), and presented strong agreement (k = 0.8). This study shows that species identified as PCs contaminants are considered inhabitants of the normal skin flora and they might become important pathogens. The results also lead to the recommendation of ABT use in laboratory routine for detecting biofilm in CoNS contaminants of PCs.

Topics: Agar; Biofilms; Blood Platelets; Coagulase; Humans; Polymerase Chain Reaction; Staphylococcal Infections; Staphylococcus

Optical density (OD) measurement is applied universally to estimate cell numbers of microorganisms growing in liquid cultures. It is a fast and reliable method but is based on the assumption that the bacteria grow as single cells of equal size and that the cells are dispersed evenly in the liquid culture. When grown in such liquid cultures, the human pathogen Staphylococcus aureus is characterized by its aggregation of single cells into clusters of variable size. Here, we show that aggregation during growth in the laboratory standard medium tryptic soy broth (TSB) is common among clinical and laboratory S. aureus isolates and that aggregation may introduce significant bias when applying standard enumeration methods on S. aureus growing in laboratory batch cultures. We provide a simple and efficient sonication procedure, which can be applied prior to optical density measurements to give an accurate estimate of cellular numbers in liquid cultures of S. aureus regardless of the aggregation level of the given strain. We further show that the sonication procedure is applicable for accurate determination of cell numbers using agar plate counting of aggregating strains.

Topics: Agar; Caseins; Colony Count, Microbial; Culture Media; Humans; Protein Hydrolysates; Sonication; Spectrophotometry; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Animals; Anti-Bacterial Agents; Bacteriological Techniques; Cattle; Cattle Diseases; Culture Media; Denmark; England; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Scotland; Sensitivity and Specificity; Staphylococcal Infections

The aim of this work was to evaluate the perfomance of agar-gelatin (AG) composites and AG-containing 45S5 bioactive glass (BG) microparticles (AGBG) in relation to their water uptake capacity, sustained release of a drug over time, and antibacterial effects. The composites were fabricated by the gel-casting method. To impart the local drug release capacity, vancomycin hydrochloride (VC) was loaded in the composites in concentrations of 0.5 and 1 mg ml(-1). VC release was assessed in distilled water at 37 °C up to 72 h and quantified spectrophotometrically. The antibacterial activity of composites was evaluated by the inhibition zone test and the plate count method. The experiments were performed in vitro up to 48 h on three staphylococcus strains: Staphylococcus aureus ATCC29213, S. aureus ATCC6538 and Staphylococcus epidermidis ATCC12228. The results showed that the addition of BG to AG composites did not affect the degree of water uptake. The release of VC was significantly affected by the presence of BG. VC release was higher from AGBGVC films than from AGVC ones over prolonged incubation times. Bacterial inhibition zones were found around the composites. The halos were larger when the cells were put in contact with AGVC composites than when they were put in contact with AGBGVC ones. Nevertheless, the viable count method demonstrated that the composites inhibited Staphylococcus cell growth with no statistical differences. In conclusion, the addition of BG did not reflect an improvement in the parameters studied. On the other hand, composites loaded with VC would have a role in prophylaxis against bacterial infection.

Topics: Agar; Anti-Bacterial Agents; Calibration; Drug Delivery Systems; Gelatin; Glass; Humans; Materials Testing; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Spectrophotometry; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus epidermidis; Vancomycin; Water

Small-colony variants (SCVs) are slow-growing subpopulations of various auxotrophic bacterial strains. Thymidine-dependent SCVs (TD-SCVs) are unable to synthesize thymidine; hence, these variants fail to grow in a medium without thymidine. In this study, we used 10 TD-SCVs of Staphylococcus aureus, of which four strains possessed mecA. We compared the efficacy of a newly modified medium containing thymidine for the detection of TD-SCVs of methicillin-resistant S. aureus (MRSA) to the efficacy of routinely used laboratory media. We observed that none of the 10 TD-SCVs of S. aureus grew in Mueller-Hinton agar, and four TD-SCVs of MRSA failed to grow on all MRSA screening media, except for the ChromID™ MRSA medium. Laboratory tests conducted using medium with thymidine incorporated showed that thymidine did not affect the minimum inhibitory concentrations of oxacillin and cefoxitin for clinical isolates of S. aureus, and was able to detect MRSA, including TD-SCVs. These findings showed that thymidine-incorporated media are able to detect TD-SCVs of MRSA without altering the properties of other clinically isolated MRSA strains.

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Cefoxitin; Culture Media; Humans; Methicillin Resistance; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxacillin; Penicillin-Binding Proteins; Pilot Projects; Staphylococcal Infections; Thymidine

We compared the diagnostic performance of two chromogenic media, Brilliance MRSA 2 agar (Thermo Fisher Scientific) and ChromID MRSA agar (bioMérieux), for MRSA confirmation of 239 Staphylococcus aureus isolates from clinical, animal and food samples. Statistically significant differences were not observed between MRSA confirmation by mecA/mecC PCR, and by culture in both chromogenic media. However, a statistically significant difference was observed between the results obtained by both chromogenic media (p = 0.003). Segregated analysis of the results depending on the origin of the isolates (clinical, animal, and food) revealed a significant lower performance in the MRSA confirmation of food-derived isolates by using Brilliance MRSA 2 agar in comparison to PCR confirmation (p = 0.003) or ChromID MRSA agar (p<0.001). Both chromogenic media provided a good diagnostic performance for detection of MRSA isolates of human and animal origin. In conclusion, the use of chromogenic agar plates for MRSA confirmation of S. aureus isolates can provide a good diagnostic performance (sensitivity >92% and specificity >89%) regardless of the type of chromogenic media used or the origin of the S. aureus isolates. However, our results revealed a lower diagnostic performance for MRSA confirmation of S. aureus isolates from food samples by using Brilliance MRSA 2 agar.

Topics: Agar; Animals; Chromogenic Compounds; Culture Media; Food Microbiology; Humans; Methicillin-Resistant Staphylococcus aureus; Microbiological Techniques; Polymerase Chain Reaction; Sensitivity and Specificity; Staphylococcal Infections

Three chromogenic media, chromID MRSA SMART (SMART), chromID MRSA first generation (chromID), and Brilliance MRSA (OX2), were evaluated for methicillin-resistant Staphylococcus aureus (MRSA) screening using 1,220 samples. The sensitivity at 24 h was significantly better with the SMART agar (66.4%) than that with chromID agar (50.5%). Enrichment and incubation until 48 h are still needed for an optimal yield.

Topics: Agar; Chromogenic Compounds; Culture Media; Hospitals; Humans; Mass Screening; Methicillin-Resistant Staphylococcus aureus; Prospective Studies; Sensitivity and Specificity; Staphylococcal Infections

BHI agars supplemented with vancomycin 4 (BHI-V4) and 3 (BHI-V3) mg/liter have been proposed for screening vancomycin intermediately susceptible Staphylococcus aureus (VISA) and heteroresistant (hVISA) phenotypes, respectively, but growth interpretation criteria have not been established. We reviewed the growth results (CFU) during population analysis profile-area under the curve (PAP-AUC) of consecutive methicillin-resistant Staphylococcus aureus (MRSA) blood isolates, which were saved intermittently between 1996 and 2012. CFU counts on BHI-V4 and BHI-V3 plates were stratified according to PAP-AUC interpretive criteria: <0.90 (susceptible [S-MRSA]), 0.90 to 1.3 (hVISA), and >1.3 (VISA). CFU cutoffs that best predict VISA and hVISA were determined with the use of receiver operating characteristic (ROC) curves. Mu3, Mu50, and methicillin-susceptible S. aureus (MSSA) controls were included. We also prospectively evaluated manufacturer-made BHI-V3/BHI-V4 biplates for screening of 2010-2012 isolates. The PAP-AUC of 616 clinical samples was consistent with S-MRSA, hVISA, and VISA in 550 (89.3%), 48 (7.8%), and 18 (2.9%) instances, respectively. For VISA screening on BHI-V4, a cutoff of 2 CFU/droplet provided 100% sensitivity and 97.7% specificity. To distinguish VISA from hVISA, a cutoff of 16 CFU provided 83.3% sensitivity and 94.7% specificity; the specificity was lowered to 89.5% with a 12-CFU cutoff. For detecting hVISA/VISA on BHI-V3, a 2-CFU/droplet cutoff provided 98.5% sensitivity and 93.8% specificity. These results suggest that 2-CFU/droplet cutoffs on BHI-V4 and BHI-V3 best approximate VISA and hVISA gold standard confirmation, respectively, with minimal overlap in samples with borderline PAP-AUC. Simultaneous screening for VISA/hVISA on manufacturer-made BHI-V4/BHI-V3 biplates is easy to standardize and may reduce the requirement for PAP-AUC confirmation.

Topics: Agar; Anti-Bacterial Agents; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Staphylococcal Infections; Vancomycin; Vancomycin Resistance

Brain heart infusion agar containing 3 mg/liter vancomycin (BHI-V3) was used to screen for heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA). There was markedly greater biofilm formation by isolates that grew on BHI-V3 than by strains that did not grow on BHI-V3. Increased biofilm formation by hVISA may be mediated by FnbA- and polysaccharide intercellular adhesin-dependent pathways, and upregulation of atlA and sarA may also contribute to enhanced biofilm formation by hVISA upon prolonged exposure to vancomycin.

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Biofilms; Culture Media; Gene Expression Regulation, Bacterial; Genes, Bacterial; Humans; Methicillin; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; RNA, Messenger; Staphylococcal Infections; Trans-Activators; Vancomycin; Vancomycin Resistance

This study aimed to correlate the presence of ica genes, biofilm formation and antimicrobial resistance in 107 strains of Staphylococcus epidermidis isolated from blood cultures. The isolates were analysed to determine their methicillin resistance, staphylococcal cassette chromosome mec (SCCmec) type, ica genes and biofilm formation and the vancomycin minimum inhibitory concentration (MIC) was measured for isolates and subpopulations growing on vancomycin screen agar. The mecA gene was detected in 81.3% of the S. epidermidis isolated and 48.2% carried SCCmec type III. The complete icaADBC operon was observed in 38.3% of the isolates; of these, 58.5% produced a biofilm. Furthermore, 47.7% of the isolates grew on vancomycin screen agar, with an increase in the MIC in 75.9% of the isolates. Determination of the MIC of subpopulations revealed that 64.7% had an MIC ≥ 4 μg mL-1, including 15.7% with an MIC of 8 μg mL-1 and 2% with an MIC of 16 μg mL-1. The presence of the icaADBC operon, biofilm production and reduced susceptibility to vancomycin were associated with methicillin resistance. This study reveals a high level of methicillin resistance, biofilm formation and reduced susceptibility to vancomycin in subpopulations of S. epidermidis. These findings may explain the selection of multidrug-resistant isolates in hospital settings and the consequent failure of antimicrobial treatment.

Topics: Adult; Agar; Aged; Biofilms; Cross Infection; Culture Media; Female; Humans; Infant; Infant, Newborn; Male; Methicillin Resistance; Microbial Sensitivity Tests; Middle Aged; Operon; Polymerase Chain Reaction; Staphylococcal Infections; Staphylococcus epidermidis; Tertiary Care Centers; Vancomycin; Vancomycin Resistance

Topics: Agar; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Staphylococcal Infections

This study aimed at testing the applicability of mannitol salt agar (MSA), a medium generally used in human medicine for differentiating Staphylococcus aureus from coagulase-negative staphylococci (CNS), for culturing bovine-associated CNS species. All test isolates from a comprehensive collection of well-identified CNS species, including both reference strains and field isolates, were able to grow. Subsequently, bulk milk samples and teat apex swabs were used to examine the capability of MSA for yielding CNS under field conditions. Sixty-nine and 47 phenotypically different colonies were retrieved from bulk milk and teat apices, respectively. The majority of isolates from teat apices were staphylococci, whereas in bulk milk, staphylococci formed a minority. After 24h of growth, recovery of separate colonies of CNS was much more convenient on MSA compared to a non-selective blood agar. The results of this study indicate that MSA is a suitable medium for both growth and recovery of bovine-associated CNS.

Topics: Agar; Animals; Bacteriological Techniques; Cattle; Cattle Diseases; Coagulase; Dairying; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Mannitol; Milk; Species Specificity; Staphylococcal Infections; Staphylococcus

V.A.C.(®) GranuFoam™ therapy is regularly used in the surgical therapy of infected wounds and soft tissue injuries. Silver nanoparticles can destroy bacterial cell walls and inhibit enzymes for cell replication. Silver dressings are therefore successfully used for many indications in wound therapy. In this study, we investigated the antimicrobial potency of ionic silver released from the silver-coated V.A.C.(®) GranuFoam™ during vacuum therapy. Silver dressing was exposed to agar plates populated with bacteria to measure silver release.. A total of 15 agar plates colonised with either Staphylococcus aureus populations or with Staphylococcus epidermidis, were loaded with V.A.C. GranuFoam Silver(®) Dressing polyurethane foam (KCI, San Antonio, Texas). Each of 13 pieces of silver-coated foam was applied to an agar plate. Two plates were loaded with conventional black foam without any coating. After connecting to a vacuum pump, the vacuum therapy of the 15 plates lasted 5 days. The zone of inhibition of bacterial growth around the foam was measured daily. Silver release was also determined as a function of time.. At each time point, there was evidence of silver in the agar independent of bacterial colonisation. The S. aureus agar showed a consecutive increase in silver concentration from baseline upon 48 h after exposure to the negative pressure of V.A.C. therapy. An increasing mean silver level after 48, 72 and 96 h was measured under V.A.C. therapy with a peak value after 120 h. In contrast, the results from the S. epidermidis plates did not follow a linear pattern. At the beginning of vacuum therapy, we documented a rise in silver concentration. After 48-96h, the silver levels fluctuated. A maximum zone of inhibition in both bacterial colonised plates (S. aureus and S. epidermidis) was found 39 h after the start of the V.A.C. GranuFoam Silver(®) therapy.. From our results, we confirmed the antimicrobial effect of the silver ions against S. aureus and S. epidermidis under continuous V.A.C. GranuFoam(®) Silver therapy with a negative pressure of 25 mmHg. Furthermore we could quantify the amounts of silver, which were released from the foam under negative pressure as a function of time.

Topics: Agar; Anti-Bacterial Agents; Colony Count, Microbial; Humans; Occlusive Dressings; Silver Compounds; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus epidermidis; Vacuum; Wound Healing; Wound Infection

We compared 2 chromogenic media (Oxoid Brilliance MRSA 2 agar [Thermo Fisher Scientific] and MRSA-ID [bioMérieux]) for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in 1,368 hospital samples. For both media, broth enrichment was essential to obtain satisfactory diagnostic performance. Although with direct cultures only, the diagnostic performance (particularly sensitivity) of Brilliance MRSA 2 agar appears better than that of MRSA-ID, no difference in sensitivity or specificity between the media was detected after inclusion of an enrichment step.

Topics: Agar; Bacteriological Techniques; Chromogenic Compounds; Color; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections

Commercially available selective media for methicillin-resistant Staphylococcus aureus (MRSA) were tested for the detection and isolation of methicillin-resistant Staphylococcus pseudintermedius (MRSP).. Five different screening agars [mannitol salt agar with oxacillin and BD BBL™ Chromagar™ MRSA (BD Diagnostics); chromID™ MRSA agar (bioMérieux); Oxacillin resistance screening agar base (ORSAB); and Brilliance MRSA agar (Oxoid)] were analysed for the detection of MRSP. Bacteria that may be isolated together with MRSP and may grow on the screening agars were included in the study to determine possible interference with the growth of MRSP. MRSP grew well on all selective media except on BD BBL™ Chromagar™ MRSA (BD Diagnostics) and chromID™ MRSA agar (bioMérieux), on which a low to moderate growth rate was noted.. ORSAB (Oxoid) and Brilliance MRSA agar (Oxoid) are most suitable for the detection and isolation of MRSP from clinical material.. The importance of MRSP in veterinary medicine is increasing. Diagnostic systems are needed to detect MRSP carrier as soon as possible. This study provides information about selected MRSA screening agars for the detection of MRSP to the clinical microbiologists.

Topics: Agar; Animals; Carrier State; Culture Media; Dog Diseases; Dogs; Methicillin Resistance; Methicillin-Resistant Staphylococcus aureus; Oxacillin; Staphylococcal Infections; Staphylococcus

A new automated closed tube PCR assay, the GenomEra(™) MRSA/SA Diagnose (Abacus Diagnostica Oy, Finland) was evaluated for rapid confirmation of methicillin-resistant Staphylococcus aureus (MRSA) from cultured screening specimens. The ability of the assay to detect genotypically different MRSA strains was studied with a collection of 304 MRSA isolates covering 68 spa types. The specificity was investigated with a collection of 146 non-MRSA staphylococcus isolates. The usefulness of the assay for clinical purposes was assessed by a sequential combination of MRSA screening culture and confirmation of the colonies with the GenomEra MRSA/SA Diagnose assay. A total of 145 suspected MRSA colonies on chromogenic plates were analyzed this way. All MRSA isolates from the culture collection and from the clinical screening specimens were confirmed as MRSA with the GenomEra MRSA/SA Diagnose assay and none of the non-MRSA staphylococci caused false-positive results, which indicates both sensitivity and specificity of 100%. The combination of GenomEra MRSA/SA Diagnose with preceding culture on selective MRSA agar permitted MRSA confirmation within 24 h. This practice offers a reliable and quick detection of MRSA that is also suitable in areas where several strain types cause epidemics.

Topics: Agar; Chromogenic Compounds; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Molecular Diagnostic Techniques; Polymerase Chain Reaction; Sensitivity and Specificity; Staphylococcal Infections

We evaluated the use of a chromogenic selective medium (MRSA ID) as a useful tool for the detection of methicillin-resistant Staphylococcus aureus (MRSA) in cystic fibrosis (CF) patient samples. Fifty-four MRSA isolates were detected by MRSA ID, while only 24/54 (44%) (odds ratio [OR], 2.79; 95% confidence interval [CI], 1.63 to 4.76) were detected by conventional methods. A chromogenic selective medium for MRSA detection may improve its surveillance in CF patients.

Topics: Agar; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Cystic Fibrosis; Humans; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections

A total of 1204 meticillin-resistant Staphylococcus aureus (MRSA) screens (3340 individual swabs) were tested to evaluate a staphylococcal cassette chromosome mec (SCCmec) real-time PCR. In total, 148 (12.3 %) of the screens were MRSA-positive, where 146 (12.1 %) were MRSA-positive by the SCCmec real-time PCR assay. In contrast, 128 (10.6 %) screens were MRSA-positive by culture. One hundred and twenty-six (10.5 %) of the screens were positive by both culture and PCR. Twenty of the 1204 screens (1.66 %) were negative by culture but positive by PCR; these samples were sequenced. In 14 of the cases, a homology search confirmed the sequence as SCCmec, indicating that these samples could be considered true positives. Two of the 1204 (0.2 %) screens were positive by culture and negative by PCR. The mean turnaround time (TAT) for PCR-negative swabs was 6 h 12 min and for PCR-positive swabs was 6 h 48 min. In comparison, for culture-negative swabs the mean TAT was 29 h 30 min and for culture-positive swabs was 69 h. The cost per swab for routine culture was £0.41 (€0.48) and that of the real-time PCR assay was £2.35 (€2.75). This optimized, in-house, inexpensive, real-time PCR test maintained a very high sensitivity and specificity when evaluated under real-time laboratory conditions. The TAT of this real-time PCR assay was substantially lower than that of chromogenic culture. It was also maintained throughout the entire process, which can be taken as an indirect measure of test performance. This study showed that implementation of a molecular test can be achieved with limited resources in a standard microbiology laboratory.

Topics: Agar; Bacteriological Techniques; Chromogenic Compounds; Culture Media; DNA, Bacterial; Genes, Bacterial; Humans; Methicillin-Resistant Staphylococcus aureus; Polymerase Chain Reaction; Sensitivity and Specificity; Sequence Analysis, DNA; Staphylococcal Infections; Time Factors

A total of 32 Staphylococcus epidermidis isolates from indwelling device-related infections such as endophthalmitis following intraocular lens (IOL) implantation, intravenous catheter-related sepsis and orthopaedic implant infections, were studied for slime production and adherence to artificial surfaces. Of these, 21 (65.6%) isolates were slime positive by the Congo Red agar method and 24 (75%) were adherent to artificial surfaces by the quantitative slime test. The majority (19 out of 24; 79.1%) of the adherent bacteria were slime producers. Antibody to slime raised in rabbits was able to inhibit the adherence of all 24 bacteria designated as adherent by our quantitative test. It seems that slime is indispensable for the sessile mode of attachment, leading further to the development of biofilms on the indwelling devices.

Topics: Adhesiveness; Agar; Animals; Biofilms; Catheters; Congo Red; Humans; Myxococcales; Prostheses and Implants; Rabbits; Staphylococcal Infections; Staphylococcus epidermidis

Detection of Staphylococcus aureus isolates with intermediate vancomycin susceptibility (VISA) and heteroresistance (hVISA) remains problematic. The population analysis profile/area under the curve (PAP/AUC) is the gold standard but is cumbersome. We compared the performance of two Etest screening methods (macromethod [MAC] and glycopeptide resistance detection [GRD]) plus brain heart infusion (BHI) agars supplemented with 3 (BHI-V3) or 4 (BHI-V4) mg/liter vancomycin in detecting hVISA and/or VISA phenotypes. Etest hVISA screenings were done in parallel for 485 saved methicillin-resistant S. aureus (MRSA) blood isolates according to the manufacturer's instructions. The PAP/AUC was measured for all isolates according to the modified method. PAP/AUC test isolate/Mu3 ratios of <0.9, 0.9 to 1.3, and >1.3 were considered positive for susceptible MRSA (S-MRSA), hVISA, and VISA, respectively. PAP/AUC revealed seven VISA and 33 hVISA phenotypes. MAC screening was positive for 30 (75.0%) hVISA/VISA and 49 (11.0%) S-MRSA isolates. GRD screening was positive for 28 (70.0%) hVISA/VISA and 63 (14.2%) S-MRSA isolates. Growth on BHI-V3 was noted in all hVISA/VISA and 24 (5.4%) S-MRSA isolates. Growth on BHI-V4 was noted in all VISA and four (12.1%) hVISA isolates. None of the S-MRSA isolates grew on BHI-V4 agar. The sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values were 75.0%, 89.0%, 38.0%, and 97.5% for MAC; 70.0%, 85.8%, 30.8%, and 97.0% for GRD; 100%, 94.6%, 62.5%, and 100% for BHI-V3; and 100, 99.2%, 63.6%, and 100% for BHI-V4 (for detecting VISA). These findings suggest that both Etest screening methods have excellent NPV, but positive results require confirmation. BHI-V3 and BHI-V4 agars provide more precise identification of hVISA and VISA, respectively; they may be reasonable alternatives to PAP/AUC.

Topics: Agar; Culture Media; Humans; Mass Screening; Microbial Sensitivity Tests; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus; Vancomycin Resistance

Topics: Agar; Animals; Anti-Bacterial Agents; Bacteriological Techniques; Carrier State; Culture Media; Ear; Mass Screening; Methicillin-Resistant Staphylococcus aureus; Nose; Oxacillin; Sacrum; Sensitivity and Specificity; Staphylococcal Infections; Swine

A novel chromogenic medium, Spectra MRSA (Remel, Lenexa, KS), was designed to detect methicillin-resistant Staphylococcus aureus (MRSA) rapidly and more efficiently than traditional media (i.e., tryptic soy agar with 5% sheep blood [SBA] and mannitol salt agar [MSA]). A multicenter study (including four clinical trial sites and the Medical College of Wisconsin [MCW] Milwaukee, WI) compared the performance characteristics of Spectra MRSA to those of the traditional media for the detection of MRSA. For this study, 767 nasal swab specimens from the multicenter study (traditional medium used, SBA) and 667 nasal swab specimens from MCW (traditional medium used, MSA) were plated on each test medium and examined after 24 and 48 h of incubation. At 24 h, the sensitivity and the specificity of each medium were as follows: in the multicenter study, 95.4% and 99.7%, respectively, for Spectra MRSA and 93.6% and 100%, respectively, for SBA; at MCW, 95.2% and 99.5%, respectively, for Spectra MRSA and 88.7% and 94.0%, respectively, for MSA. The positive predictive values of each medium at 24 h were as follows: in the multicenter study, 98.1% for Spectra MRSA and 100% for SBA; at MCW, 95.2% for Spectra MRSA and 60.4% for MSA. In our evaluation, we found that Spectra MRSA was able to rapidly identify and differentiate methicillin-resistant S. aureus from methicillin-susceptible S. aureus on the basis of the utilization of chromogens that result in denim blue colonies, thus eliminating the need for biochemical analysis and antimicrobial susceptibility testing. Extending the incubation beyond 24 h did not significantly improve the recovery of MRSA and resulted in decreased specificity.

Topics: Agar; Bacteriological Techniques; Chromogenic Compounds; Color; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Predictive Value of Tests; Sensitivity and Specificity; Staphylococcal Infections

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) is responsible for nosocomial and community-acquired infections. Hence, rapid and accurate laboratory diagnosis of MRSA is a vital constituent of control measures. The present study evaluated five different methods for the identification of MRSA. A total of 207 S. aureus clinical isolates that consisted of 89 MRSA and 118 methicillin-susceptible S. aureus (MSSA) strains confirmed by PCR were tested. MRSA strains were evaluated by five different methods: chromogenic MRSA agar (CMRSA), oxacillin resistance screening agar base (ORSAB), mannitol salt oxacillin agar (MSO), mannitol salt cefoxitin agar with two different concentrations of cefoxitin [4 microg/ml (MSC-4) and 6 microg/ml (MSC-6)]. The results of the different methods were compared to mecA PCR as the gold standard. MSC-6 showed only six false-positive MRSA in comparison with PCR. The sensitivities and specificities of MSC-6, MSC-4, MSO-4, ORSAB, and CMRSA were as follows: 98.9/94.9%, 100/83.1%, 89.9/87.3%, 97.8/96.6%, and 95.5/94.9%, respectively. In comparison with PCR, it was found that both MSC-6 and ORSAB were relatively the least expensive screening tests ($0.70 and $1.00, respectively). In conclusion, all methods were comparable, but MSC-6 was the least expensive medium for MRSA screening.

Topics: Agar; Anti-Bacterial Agents; Cefoxitin; Culture Media; Humans; Methicillin; Methicillin Resistance; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Oxacillin; Polymerase Chain Reaction; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

(1) To determine whether rapid screening with polymerase chain reaction (PCR) assays leads to the earlier isolation of patients at risk for methicillin-resistant Staphylococcus aureus (MRSA) colonization, (2) to assess compliance with routine MRSA screening protocols, (3) to confirm the diagnostic accuracy of the Xpert MRSA real-time PCR assay (Cepheid) by comparison with culture, and (4) to compare turnaround times for PCR assay results with those for culture results.. Before-and-after study conducted in a 700-bed acute tertiary care referral hospital. Study periods were (1) a 5-week period before PCR testing began, (2) a 10-week period when the PCR assay was used, and (3) a 5-week period after PCR testing was discontinued.. Among 489 at-risk patients, MRSA was isolated from 20 (33%) of 60 patients during period 1, 77 (22%) of 349 patients during period 2, and 18 (23%) of 80 patients during period 3. Twenty-two (27%) of 82 at-risk patients were not screened during period 1, compared with 40 (10%) of 389 at-risk patients not screened during period 2 (P < .001). More MRSA-positive patients were preemptively isolated during periods 1 and 3 compared with period 2 (34 [24%] of 140 vs 28 [8%] of 389; P < .001); however, more MRSA-positive patients were isolated after notification of MRSA-positive results during period 2 (47 [13%] of 349) compared with periods 1 and 3 (2 [1%] of 140; P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value of the PCR assay were 95%, 97%, 82%, and 99%, respectively. The mean turnaround time from receipt of specimens in the laboratory to PCR assay result was 2.6 hours.. Rapid screening with the Xpert MRSA PCR assay facilitated compliance with screening policies and the earlier isolation of MRSA-positive patients. Discrepant results confirm that PCR testing should be used as a screening tool rather than as a diagnostic tool.

Topics: Agar; Bacterial Typing Techniques; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Guideline Adherence; Humans; Mass Screening; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Polymerase Chain Reaction; Predictive Value of Tests; Risk Factors; Sensitivity and Specificity; Staphylococcal Infections; Time Factors

Pre-emptive isolation of suspected methicillin-resistant Staphylococcus aureus (MRSA) carriers is considered essential for controlling the spread of MRSA, but noncolonized patients will be isolated unnecessarily as a result of a delay in diagnosis of 3-5 days with conventional cultures. We determined costs per isolation day avoided, and incremental costs of rapid MRSA screening tests when added to conventional screening, but with decisions on isolation measures based on PCR results. A prospective multicentre study evaluating BD GeneOhm MRSA PCR (`IDI') (BD Diagnostics, San Diego, CA, USA), Xpert MRSA (`GeneXpert') (Cepheid, Sunnyvale, CA, USA) and chromogenic agar (MRSA-ID) (bioMérieux, Marcy-l'Etoile, France) was performed in 14 Dutch hospitals. Among 1764 patients at risk, MRSA prevalence was 3.3% (n=59). Duration of isolation was 19.7 and 16.1 h with IDI and GeneXpert, respectively, and would have been 30.0 and 76.2 h when based on chromogenic agar and conventional cultures, respectively. Negative predictive values (at a patient level) were 99.5%, 99.1% and 99.5% for IDI, GeneXpert and chromogenic agar, respectively. Numbers of isolation days were reduced by 60% and 47% with PCR-based and chromogenic agar-based screening, respectively. The cost per test was €56.22 for IDI, €69.62 for GeneXpert and €2.08 for chromogenic agar, and additional costs per extra isolation day were €26.34. Costs per isolation day avoided were €95.77 (IDI) and €125.43 (GeneXpert). PCR-based decision-making added €153.64 (IDI) and €193.84 (GeneXpert) per patient to overall costs and chromogenic testing would have saved €30.79 per patient. Rapid diagnostic testing safely reduces the number of unnecessary isolation days, but only chromogenic screening, and not PCR-based screening, can be considered as cost saving.

Topics: Agar; Carrier State; Chromogenic Compounds; Cost-Benefit Analysis; Cross Infection; Diagnostic Tests, Routine; Health Care Costs; Humans; Methicillin-Resistant Staphylococcus aureus; Patient Isolation; Polymerase Chain Reaction; Predictive Value of Tests; Prospective Studies; Staphylococcal Infections

Spectra MRSA agar (Remel, Lenexa, KS), a novel chromogenic medium originally developed to detect methicillin-resistant Staphylococcus aureus (MRSA) from nasal swabs, was evaluated in this multicenter study for the detection of MRSA from positive blood cultures exhibiting Gram-positive cocci upon initial Gram staining.

Topics: Agar; Bacteriological Techniques; Blood; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections

MRSASelect agar (Bio-Rad, Redmond, WA) was evaluated for its performance in detecting MRSA directly from positive blood cultures containing Gram-positive cocci in clusters. Agar plates were evaluated for the presence of pink colonies at 18 to 24 h. Results were compared to organism identification by using standard laboratory methods. Confirming coagulase on pink isolates, the sensitivity and specificity were both 99%.

Topics: Agar; Bacteriological Techniques; Blood; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections

To evaluate methicillin-resistant S. aureus (MRSA) detection methods, we compared (a) mannitol salt agar with cefoxitin (MSA-FX), (b) MRSASelect agar (Bio-Rad), (c) MRSA ID (bioMerieuex), and (d) CHROMagar MRSA (BD Diagnostics) as selective media for culturing nasal swab specimens collected from intensive care unit (ICU) patients and healthcare personnel. A total of 99 (17.1%) cases of MRSA were recovered from 578 specimens. Four (5.5%) cases were identified from healthcare personnel and 95 (18.8%) were from ICU patients. The sensitivity of MSA-FX, MRSASelect, MRSA ID, and CHROMagar MRSA was 83.8, 87.9, 80.8, and 84.8% after 18 hr; 92.9, 94.9, 90.9, and 91.9% after 24 hr; and 96.0, 100, 99.0, and 99.0% after 48 hr, respectively. The specificity of MSA-FX, MRSASelect, MRSA ID, and CHROMagar MRSA was 97.7, 99.0, 98.7. and 99.8% after 18 hr; 97.1, 98.5, 98.1, and 99.5% after 24 hr; and 95.2, 97.7, 97.9, and 99.0% after 48 hr, respectively. In conclusion, all four media showed good results after the 24 hr readings, but MRSA ID and CHROMagar MRSA media required readings at 48 hr due to increased sensitivity at this time point.

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Blotting, Western; Cefoxitin; Chromogenic Compounds; Health Personnel; Humans; Intensive Care Units; Mannitol; Methicillin-Resistant Staphylococcus aureus; Nasal Mucosa; Penicillin-Binding Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sensitivity and Specificity; Staphylococcal Infections

The ideal identification of Staphylococcus aureus clinical isolates requires a battery of tests and this is costly in resource limited settings. In many developing countries, the tube coagulase test is usually confirmatory for S. aureus and is routinely done using either human or sheep plasma. This study evaluated Mannitol salt agar and the deoxyribonuclease (DNase) test for improving the efficiency of the tube coagulase test in resource limited settings. The efficiency of human and sheep plasma with tube coagulase tests was also evaluated.. One hundred and eighty Gram positive, Catalase positive cocci occurring in pairs, short chains or clusters were subjected to growth on Mannitol salt agar, deoxyribonuclease and tube coagulase tests. Of these, isolates that were positive for at least two of the three tests (n = 60) were used to evaluate the performance of the tube coagulase test for identification of S. aureus, using PCR-amplification of the nuc gene as a gold standard.. Human plasma was more sensitive than sheep plasma for the tube coagulase test (sensitivity of 91% vs. 81% respectively), but both plasmas had very low specificity (11% and 7% respectively). The sensitivity and specificity of the tube coagulase test (human plasma) was markedly improved when Mannitol salt agar and DNase were introduced as a tri-combination test for routine identification of Staphylococcus aureus (100% specificity and 75% sensitivity). The specificity and sensitivity of Mannitol salt agar/DNase/tube coagulase (sheep plasma) combination was 100% and 67%, respectively.. The efficiency of the tube coagulase test can be markedly improved by sequel testing of the isolates with Mannitol salt agar, DNase and Tube coagulase. There is no single phenotypic test (including tube coagulase) that can guarantee reliable results in the identification of Staphylococcus aureus.

Topics: Agar; Animals; Blood; Coagulase; Deoxyribonucleases; Developing Countries; Humans; Mannitol; Polymerase Chain Reaction; Predictive Value of Tests; Sheep; Staphylococcal Infections; Staphylococcus aureus; Uganda

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of nosocomial infections that result in extended hospital stays and increased mortality. Therefore, rapid, cost-effective techniques for surveillance and detection of MRSA are critical to the containment and prevention of the spread of MRSA within the health care environment. We examined the ability of 3 chromogenic media (Spectra MRSA, Remel, Lenexa, KS; MRSA Select, Bio-Rad, Redmond, WA; and ChromID MRSA, bioMerieux, Marcy l'Etoile, France) to detect MRSA from routine surveillance specimens following 18, 24, and 48 hours of incubation. Our results indicate that detection of MRSA using all 3 chromogenic media is optimal following 24 hours of incubation. Early examination reduced sensitivity, while extended incubation reduced specificity. In addition, Spectra MRSA identified 2 borderline oxacillin-resistant strains of S aureus that were not detected by the other 2 chromogenic agars evaluated. These strains demonstrate increased basal and inducible resistance to β-lactam antibiotics.

Topics: Agar; Anti-Bacterial Agents; Chromogenic Compounds; Cross Infection; Culture Media; Humans; Methicillin Resistance; Methicillin-Resistant Staphylococcus aureus; Nasal Mucosa; Oxacillin; Predictive Value of Tests; Staphylococcal Infections; Staphylococcus aureus

Rapid laboratory methods provide optimal support for active surveillance efforts to screen for methicillin-resistant Staphylococcus aureus (MRSA). Most laboratories struggle to determine the optimal use of resources, considering options to balance cost, speed, and diagnostic accuracy. To assess the performance of common methods, the first comparison of MRSASelect agar (MS) and CHROMagar MRSA (CA), with and without broth enrichment followed by a 24-h subculture to MS, was performed. Results were compared to those of the Xpert MRSA assay. For direct culture methods, the agreement between MS and CA was 98.8%. At 18 h, direct MS identified 93% of all positive samples from direct culture and 84% of those identified by the Xpert MRSA. For Trypticase soy broth-enriched MS culture, incubated overnight and then subcultured for an additional 24 h, the agreement with Xpert MRSA was 96%. The agreement between direct MS and Xpert MRSA was 100% when semiquantitative culture revealed a bacterial density of 2+ or greater; however, discrepancies between culture and Xpert MRSA arose for MRSA bacterial densities of 1+ or less, indicating low density as a common cause of false-negative culture results. Since 1+ or less was established as the most common MRSA carrier state, broth enrichment or PCR may be critical for the identification of all MRSA carriers who may be reservoirs for transmission. In this active-surveillance convenience sample, the use of broth enrichment followed by subculture to MS offered a low-cost but sensitive method for MRSA screening, with performance similar to that of Xpert MRSA PCR.

Topics: Agar; Arizona; Bacterial Typing Techniques; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Nasal Cavity; Polymerase Chain Reaction; Population Surveillance; Prevalence; Reproducibility of Results; Sensitivity and Specificity; Staphylococcal Infections

MRSA-carrier screening is recommended to prevent MRSA dissemination in hospitals. Rapid and specific detection of MRSA in the laboratory is a key element in enabling control measures. Our objective was to evaluate the impact of different lengths of pre-incubation in a nutritive broth and prolonged incubation of MRSA-ID, a chromogenic agar medium, on its performances for identifying MRSA in screening samples. According to our results, short-length pre-enrichments only provided a weak increase of sensitivity as compared to the absence of pre-enrichment. On the contrary, the sensitivity increase provided by an overnight pre-enrichment was significant. The prolongation of incubation in the chromogenic agar medium (48 hours instead of 24 hours) did not provide any significant increase of sensitivity but was associated with a strong and significant loss of specificity. Therefore, it seems relevant to reject prolonged incubation of selective agar media and to make a choice between the absence of pre-enrichment (faster results) and an overnight pre-enrichment (higher sensitivity), according to local epidemiology and local practices implemented for prevention.

Topics: Agar; Carrier State; Culture Media; Hospitals; Humans; Inpatients; Kinetics; Mass Screening; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections; Time Factors

In this study we evaluated the performance of the oxacillin agar screen test, and agar dilution tests using cefoxitin and oxacillin antimicrobials, to detect meticillin resistance in Staphylococcus aureus isolates. The presence of the mecA gene, detected by PCR, was used as the standard to which agar screen and agar dilution tests were compared. The best performance was obtained using the agar dilution test (99.4 % accuracy) with breakpoints of 4 mug ml(-1) for oxacillin and 8 mug ml(-1) for cefoxitin, and using the oxacillin agar screen test. Also, a strong correlation between MIC values of cefoxitin and oxacillin permits the use of either drug for detection of meticillin resistance.

Topics: Agar; Cefoxitin; Humans; Inpatients; Methicillin Resistance; Microbial Sensitivity Tests; Oxacillin; Staphylococcal Infections; Staphylococcus aureus

To evaluate methicillin-resistant Staphylococcus aureus detection, we tested in vitro four selective agars and two enrichment broths apart and in combination. Tryptone soya broth with salt, aztreonam, and cefoxitin appeared to be the most sensitive medium. This broth was superior to a phenol red mannitol broth with aztreonam and ceftizoxime.

Topics: Agar; Culture Media; Humans; Methicillin-Resistant Staphylococcus aureus; Sensitivity and Specificity; Staphylococcal Infections

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Humans; Mass Screening; Methicillin-Resistant Staphylococcus aureus; Nasopharynx; Penicillin-Binding Proteins; Sensitivity and Specificity; Staphylococcal Infections

An evaluation of Chromogenic MRSA medium (CMRSA), MRSASelect (MRSAS) and Oxacillin Resistance Screening Agar (ORSA) was performed to determine the optimum medium providing a rapid and sensitive method for methicillin-resistant Staphylococcus aureus (MRSA) detection.. A total of 632 clinical specimens were cultured on the three media in first phase of the study, while 720 clinical specimens were cultured on CMRSA and ORSA in the second phase.. The sensitivity and specificity, respectively, of the media in the first phase were: CMRSA 88.9% and 98.45%; MRSAS 92.1% and 99.1%; ORSA (24 h incubation) 68.3% and 98.8%; and ORSA (48 h incubation) 85.7% and 96.3%. In the second phase the sensitivity and specificity, respectively, were CMRSA 91.2% and 98.6%; ORSA (24 h incubation) 58.9% and 98.2%; and ORSA (48 h incubation) 85.6% and 95.6%. The positive predictive values of the two chromogenic media were higher than that for ORSA. There were fewer false-positive results with the chromogenic media (1.4% for CMRSA and 0.8% for MRSAS) compared with ORSA (3.3%).. Performing latex agglutination tests on growth from chromogenic media provides results for 93.8% of MRSA isolates within 24 h. There is a small increase in cost of chromogenic media compared with ORSA ( pound28 for MRSAS, and pound36 for CMRSA, per 1000 specimens) and direct agglutination tests ( pound80 per 1000 specimens). However early availability of MRSA screening results can reduce the burden of MRSA in hospitals because of early implementation of infection control measures.

Topics: Agar; Anti-Bacterial Agents; Chromogenic Compounds; Culture Media; Humans; Latex Fixation Tests; Methicillin Resistance; Microbial Sensitivity Tests; Oxacillin; Predictive Value of Tests; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

We describe the search toward a fast and reliable strategy to detect and confirm the presence of methicillin-resistant Staphylococcus aureus (MRSA) in screening samples. First, we evaluated the sensitivities and specificities of oxacillin resistance screening agar (ORSA) with enrichment (tryptic soy broth [TSB] and ORSA [TSB-ORSA]) and without enrichment (ORSA), MRSA ID (MRSA_ID) plates, and CHROMagar MRSA (C_MRSA) plates, all of which were inoculated with equal volumes of a suspension made by emulsifying screening swabs. Whereas the sensitivities after 48 h were similar for all media tested (77% for MRSA_ID and ORSA; 73% for C_MRSA and ORSA after enrichment [TSB-ORSA]), the specificities of MRSA_ID (98% after 24 h and 94% after 48 h) and C_MRSA (98% after 24 h and 90% after 48 h) were superior to the specificities of ORSAs (92% after 24 h and 83% after 48 h) and TSB-ORSA (86% after 24 h and 81% after 48 h). Subsequently, the performance of the Pastorex Staph-Plus agglutination test with presumptive MRSA isolates taken directly from chromogenic agars (direct_Pastorex agglutination) was compared to that of the Pastorex Staph-Plus agglutination test with isolates from blood agar subcultures (conventional_Pastorex agglutination). When the direct_Pastorex agglutination test on MRSA_ID plates was combined with Gram staining, the direct_Pastorex agglutination test with samples from MRSA_ID plates was as reliable as the conventional_Pastorex agglutination test with samples from blood agar subcultures from MRSA_ID plates. In contrast, the direct_Pastorex agglutination test with samples from C_MRSA plates gave false-negative results. Finally, we calculated the processing times of the four different strategies, namely, (i) enrichment in TSB supplemented with NaCl, subsequent culture on ORSA, and the conventional_Pastorex agglutination test; (ii) direct inoculation of ORSA combined with conventional_Pastorex agglutination test; (iii) direct inoculation of MRSA_ID plates combined with Gram staining and the direct_Pastorex agglutination test; and (iv) direct inoculation of C_MRSA plates combined with Gram staining and the direct_Pastorex agglutination test. We concluded that the use of MRSA_ID in combination with Gram staining and the direct_Pastorex agglutination test is faster and more specific than the other strategies tested.

Topics: Agar; Anti-Bacterial Agents; Chromogenic Compounds; Culture Media; Humans; Latex Fixation Tests; Methicillin; Methicillin Resistance; Microbial Sensitivity Tests; Polymerase Chain Reaction; Staphylococcal Infections; Staphylococcus aureus

Glycopeptide-intermediate Staphylococcus aureus (GISA) and heterogeneous GISA (hGISA) strains are notoriously difficult to detect in the diagnostic laboratory. The clinical importance of GISA, and particularly hGISA, will only be obvious when a definitive detection method is available. A few novel GISA and hGISA detection methods have been proposed; however, their validity has never been tested on a significant scale and in different laboratories. This study compares three screening methods for detecting GISA and hGISA strains in 12 laboratories, using a blind panel of 48 strains with known glycopeptide susceptibilities. The three screening methods used were brain heart infusion agar with 6 mg/liter vancomycin (BHIA6V) (CDC/CLSI), Mueller-Hinton agar with 5 mg/liter teicoplanin (MHA5T) (European Antimicrobial Resistance Surveillance System [EARSS]), and the macrodilution method Etest (MET) (EARSS), with population analysis profile-area under the curve analysis as the gold standard. Sensitivity and specificity were highest for MHA5T and MET, which identified 82.5% and 85.9% of strains, respectively. BHIA6V had poor sensitivity, particularly for hGISA (11.5% of strains were detected), and gave the largest interlaboratory variation in performance. MET exhibited the least interlaboratory variation. It is essential that laboratories use appropriate methods to detect GISA/hGISA strains so that the prevalence and clinical importance of these strains can be assessed properly.

Topics: Agar; Anti-Bacterial Agents; Bacterial Typing Techniques; Culture Media; Drug Resistance, Bacterial; Glycopeptides; Humans; Microbial Sensitivity Tests; Staphylococcal Infections; Staphylococcus aureus; Teicoplanin; Vancomycin

Mannitol salt agar (MSA), CHROMagar Staph aureus (CSA) and CHROMagar MRSA (CSA-MRSA) were evaluated with nasal surveillance specimens for their ability to detect Staphylococcus aureus and meticillin-resistant S. aureus (MRSA). CSA was found to be more sensitive than MSA in detecting S. aureus (98 versus 84.3 %; P=0.03). CSA and CSA-MRSA were equivalent in the ability to detect MRSA at 24 h (89.7 versus 87.2 %) and at 48 h (94.9 versus 94.9 %). When combined with Staphaurex slide confirmation testing, both CSA and CSA-MRSA were highly specific (100 %) media for detecting MRSA from nasal swab specimens.

Topics: Agar; Anti-Bacterial Agents; Cefoxitin; Chromogenic Compounds; Culture Media; Humans; Mannitol; Methicillin; Methicillin Resistance; Microbial Sensitivity Tests; Nasal Mucosa; Species Specificity; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Members of the genus Staphylococcus are among the most important human pathogens, and strains demonstrating resistance to methicillin are an increasing problem worldwide, both within and outside of hospital environments. The objective of this study was to evaluate the use of variations of agar screening tests with cefoxitin and oxacillin to detect methicillin resistance in staphylococcal isolates. The agar screening test with cefoxitin (4 microg/ml) showed 99.4% accuracy for detecting both S. aureus and coagulase-negative staphylococci. The performance of the agar screening test with cefoxitin (4 microg/ml) either equaled or was superior to the other agar screening test variations evaluated and can be used to characterize the presence of the mecA gene among staphylococcal species.

Topics: Agar; Anti-Bacterial Agents; Bacterial Proteins; Cefoxitin; Humans; Methicillin Resistance; Microbial Sensitivity Tests; Oxacillin; Penicillin-Binding Proteins; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus

A novel chromogenic medium for the detection of meticillin-resistant Staphylococcus aureus (MRSA), MRSASelect (Bio-Rad), was evaluated with clinical samples in a public health laboratory in The Netherlands. In total, 3000 samples were tested in the period January to March 2005, including 972 nose, 972 throat, 968 perineum, and 88 wound or urine samples. Presumptive MRSA colonies appeared pink/mauve on the MRSASelect medium. The performance of MRSASelect medium was compared with the routine screening method. Evaluation of the colony morphology showed that all confirmed MRSA isolates grew as pink/mauve colonies. None of the white colonies were MRSA strains. The number of false-positive pink/mauve colonies increased after prolonged incubation from 20 to 48 h. The specificity decreased from 92 % after 20 h incubation to 89 % after 48 h incubation. In total 70 MRSA strains were isolated, 55 of which were detected by the MRSASelect medium and 55 were detected by the routine screening method. Sensitivity was 78.6 % for both test procedures, and specificities were 99.5 and 100 %, respectively for the MRSASelect medium and the routine screening method. The addition of an enrichment broth to the MRSASelect medium increased the number of MRSA strains detected by 12 %. In total, 18 patients were MRSA positive, 4 of these were detected by the MRSASelect medium only and 1 was detected by the routine screening method only. Sensitivity on patient level was 94.4 and 77.8 % for the MRSASelect medium and the routine screening method, respectively, while specificities were 99.7 and 99.0 %.

Topics: Agar; Chromogenic Compounds; Culture Media; Methicillin Resistance; Netherlands; Staphylococcal Infections; Staphylococcus aureus; Time Factors

Topics: Acetamides; Acute Disease; Adult; Agar; Anti-Bacterial Agents; Bone Marrow Transplantation; Drug Resistance; Humans; Immunocompromised Host; Leukemia, Myeloid; Linezolid; Male; Microbial Sensitivity Tests; Oxazolidinones; Staphylococcal Infections; Staphylococcus epidermidis; Staphylococcus haemolyticus; Vancomycin

MRSA ID was evaluated for its ability to identify methicillin-resistant Staphylococcus aureus. A well-defined collection of staphylococci was used (n = 998). The sensitivity after 24 h was 96.4%, increasing to 98.8% after 48 h. The specificity was 98.2% after 24 h and decreased to 89.7% after 48 h.

Topics: Agar; Anti-Bacterial Agents; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Humans; Methicillin; Methicillin Resistance; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

Screening for staphylococci among various patient populations has become important for appropriate therapeutic management and for control of nosocomial infections. The purpose of this study is to evaluate the in vitro sensitivity and specificity of a chromogenic agar medium, S. aureus ID (bioMérieux, France), for the identification of Staphylococcus aureus.. A well-defined collection of S. aureus and coagulase-negative staphylococci (CNS) was used. The methicillin-resistant S. aureus (MRSA) isolates were collected in The Netherlands and all had a unique typing pattern. The methicillin-susceptible S. aureus (MSSA) and CNS were isolated from cultures of blood. The isolates were inoculated on Columbia agar plates with 5% sheep blood and incubated for 24 h at 35 degrees C. From the resulting cultures, a suspension of 0.5 McFarland was made and subsequently 10 mul was streaked on a S. aureus ID plate using a sterile loop. The results were read after 24 h and 48 h of incubation at 35 degrees C. Growth of colonies showing green coloration was considered to be positive (indicating S. aureus).. A total of 519 S. aureus strains were tested (249 MSSA, 270 MRSA). The sensitivity to detect S. aureus was 96.5% (501/519) after 24 h and 97.5% (506/519) after 48 h. A total of 478 CNS were tested. The specificity was 98.5% (471/478) after 24 h and 98.3% (470/478) after 48 h. The differences between 24 h and 48 h incubation were not statistically significant.. S. aureus ID is highly sensitive and specific to differentiate between S. aureus and CNS in vitro. Since the performance does not significantly differ between 24 h or 48 h of incubation, samples need only 1 day of incubation before optimal results can be obtained.

Topics: Agar; Anti-Bacterial Agents; Bacterial Typing Techniques; Chromogenic Compounds; Coagulase; Culture Media; Humans; Methicillin; Methicillin Resistance; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

To investigate the use of mannitol salt agar (MSA) supplemented with acriflavine for selective growth and quantification of Staphylococcus aureus from flushed dairy manure wastewater (FDMW).. Minimal inhibitory concentrations of acriflavine in MSA were determined by comparing the growth of S. aureus subsp. aureus (ATCC 33591) and Staphylococcus epidermidis (ATCC 155) in pure culture. Acriflavine concentrations of 1.3, 1.4 and 1.5 mg l(-1) reduced CFU of S. epidermidis by 43%, 55% and 87%, respectively, while CFU of S. aureus subsp. aureus were only reduced by 15%, 20% and 26% at the respective concentrations of acriflavine. MSA supplemented with 1.5 mg l(-1) acriflavine was tested for selective growth of indigenous S. aureus from three grab samples of FDMW. Acriflavine concentrations of 1.5 mg l(-1) reduced background flora without significantly reducing (P < 0.05) indigenous S. aureus counts.. Acriflavine-supplemented MSA provides an effective media for selective growth and quantification of indigenous S. aureus from FDMW in the presence of high levels of background microflora.. S. aureus is implicated for mastitis infections in dairy cows. Therefore, a reliable means for monitoring and detecting the organism in FDMW provides a tool for measuring the effectiveness of treatment for reducing S. aureus levels and implementing flushwater recycling without affecting herd health.

Topics: Acriflavine; Agar; Animals; Bacteriological Techniques; Cattle; Culture Media; Dairying; Fresh Water; Mannitol; Manure; Mastitis, Bovine; Staphylococcal Infections; Staphylococcus aureus; Waste Disposal, Fluid

Two strains of methicillin-resistant Staphylococcus aureus (MRSA), termed epidemic strains (EMRSA-15 and EMRSA-16), were used to evaluate the antimicrobial and barrier effect of four silver dressings (two silver donating and two non-silver-donating) available in the UK at the time of the study.. The moist surface of a blood agar plate was covered with 10(6) colony-forming units of the respective strain of MRSA, and dressings were applied to the surface and incubated at 37 degrees C for different time periods and the upper and lower surfaces subcultured for residual growth.. The nanocrystalline dressings (silver donating) were effective as a barrier from one hour until the study end (72 hours): no penetration of EMRSA-15 and EMRSA-16 through the dressing occurred. Moreover, the nanocrystalline dressings showed some antimicrobial activity at one hour in the areas underneath and surrounding the dressing until the study end. The remaining two dressings had no barrier effect and only demonstrated limited antimicrobial activity after 24 hours.. This in vitro study suggests that the nanocrystalline dressings are more effective than other silver dressings in terms of providing a barrier function and antimicrobial activity against EMRSA-15 and EMRSA-16.

Topics: Administration, Cutaneous; Agar; Anti-Infective Agents, Local; Carboxymethylcellulose Sodium; Culture Media; Drug Evaluation, Preclinical; Humans; Infection Control; Methicillin Resistance; Nanostructures; Polyesters; Polyethylenes; Silver; Staphylococcal Infections; Staphylococcus aureus; Time Factors; Wound Infection

To identify the most rapid and reliable technique for recovery and identification of Staphylococcus aureus small-colony variants (SCVs), the colonial appearance of 106 isolates representing SCVs and the normal phenotype were evaluated on two newly described chromogenic agar media. Although almost all of the SCVs grew on the chromogenic agar media, they did not exhibit a change of color. In comparison with conventional media, S. aureus ID agar (SAID; bioMerieux, La Balme Les Grottes, France) showed the most reliable results, with 49 of 53 SCVs tested growing either as an SCV colony or with a normal phenotype after only 24 h of incubation. Growth of SCVs was often not detected before 72 h of incubation on some of the media tested. In conclusion, the most accurate and rapid method to detect both the species S. aureus and the SCV phenotype is to inoculate specimens onto both Columbia blood agar and SAID.

Topics: Agar; Bacterial Typing Techniques; Bacteriological Techniques; Chromogenic Compounds; Culture Media; Humans; Phenotype; Staphylococcal Infections; Staphylococcus aureus

We used 200 sputum specimens from patients with cystic fibrosis to evaluate BBL CHROMagar Staph aureus medium (CSA; BD Diagnostics, Spark, MD). Samples were inoculated to CSA, trypticase soy blood agar (BA), and Mannitol Salt (MS; BD Diagnostics). After 18 hours of incubation, CSA detected 39 (78%) of 50 Staphylococcus aureus (SA) samples; BA detected 30 (60%); and MS detected 29 (58%). Sensitivity after overnight incubation (at least 18 hours) was 82% for CSA, 72% for BA, and 71% for MS. At 2 days, CSA detected 48 (96%) of the SA. There were 2 false-positive results on CSA (99% specificity). There were 4 (8%) minor and no major or very major discrepancies between minimum inhibitory concentration (MIC) results for isolates grown on CSA and those grown on BA. Even at early reading times, CSA was superior to conventional media for detection of SA in these very complex cultures. MICs from all SA samples can be reported 24 hours sooner, and an additional BA subculture is not needed.

Topics: Agar; Animals; Bacteriological Techniques; Chromogenic Compounds; Cystic Fibrosis; Humans; Mannitol; Reproducibility of Results; Sensitivity and Specificity; Sputum; Staphylococcal Infections; Staphylococcus aureus

The opportunistic pathogen Staphylococcus epidermidis is able to produce biofilm and to frequently cause implant infections. In recent years, it has also exhibited an increasing antimicrobial drug resistance. Here, the resistance to a panel of 16 different antibiotics in 342 clinical strains of S. epidermidis from orthopaedic implant infections has been investigated. The isolates were pheno- and genotyped for extracellular polysaccharide production, relevant to staphylococcal biofilm formation, in order to ascertain possible associations with antibiotic resistance. Approximately 10% of the isolates were found to be sensitive to all screened antibiotics. In all, 37-38% were resistant to beta-lactams such as oxacillin and imipenem, while the resistance to penicillin, ampicillin, cefazolin, cefamandole, was consistently observed in over 80% of the strains. Erythromycin- and clindamycin- resistant strains were approximately 41% and 16%, respectively. Of the isolates, 10% was resistant to chloramphenicol, 23% to sulfamethoxazole and 26% to ciprofloxacin. Resistance to vancomycin was never observed. Interestingly, exopolysaccharide-producing strains exhibited a significantly higher prevalence in the resistance to the four aminoglycosides (gentamicin, amikacin, netilmicin, tobramycin), to sulfamethoxazole and to ciprofloxacin with respect to non-producing isolates. Moreover, multiple resistance to antibiotics was more frequent among exopolysaccharide-forming strains.

Topics: Agar; Anti-Bacterial Agents; beta-Lactams; Biofilms; Clindamycin; Diffusion; Drug Resistance, Bacterial; Drug Resistance, Microbial; Erythromycin; Humans; Materials Testing; Methicillin; Orthopedics; Polysaccharides; Prostheses and Implants; Prosthesis-Related Infections; Staphylococcal Infections; Staphylococcus epidermidis

In vitro studies investigating the influence of electric DC current on bacterial detachment have demonstrated that continuous currents of only 25-125 microA stimulated staphylococcal strains to detach from surgical stainless steel. However, DC currents produce more power that has to be dissipated by the skin as compared to alternating currents. Also, an excess of ions on the steel can cause negative osteogenesis and fixation results. Therefore, it is the aim of this paper to examine whether detachment of Staphylococcus epidermidis from stainless steel surfaces in a parallel plate flow chamber can also be stimulated using electric block currents. Block currents of 15, 60 and 100 microA with different frequencies (0.1-2 Hz) and duty cycles (5-50%) were applied to induce bacterial detachment. Block currents of 100 microA cause detachment of about 76% of adhering staphylococci from stainless steel, whereas in addition the remaining bacteria are less viable, as determined by culturing the remaining bacteria on agar plates. Therewith, block current-induced detachment of adhering bacteria from stainless steel appears to be an equally promising method to prevent infection of orthopaedic fixation pins and screws than application of DC currents.

Topics: Adsorption; Agar; Bacterial Adhesion; Biocompatible Materials; Biofilms; Cell Adhesion; Electric Conductivity; Hydrogen Peroxide; Ions; Orthopedic Fixation Devices; Prostheses and Implants; Prosthesis-Related Infections; Stainless Steel; Staphylococcal Infections; Staphylococcus epidermidis; Time Factors

Active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) is among the strategies recommended by the Society for Healthcare Epidemiology of America for control of nosocomial MRSA infections. Infection control and laboratory personnel desire rapid, sensitive, and inexpensive methods to enhance surveillance activities. A multicenter study was performed to evaluate a new selective and differential chromogenic medium, BBL CHROMagar MRSA (C-MRSA) medium (BD Diagnostics, Sparks, MD), which enables recovery and concomitant identification of MRSA strains directly from nasal swab specimens taken from the anterior nares. Specimens were inoculated to C-MRSA and Trypticase soy agar with 5% sheep blood agar (TSA II, BD Diagnostics). Mauve colonies on C-MRSA at 24 h and 48 h and suspicious colonies on TSA II were confirmed as Staphylococcus aureus by Gram stain morphology and a coagulase test. In addition, the results of C-MRSA were compared to results of susceptibility testing (five different methods) of S. aureus strains isolated on TSA II. A total of 2,015 specimens were inoculated to C-MRSA and TSA II. Three hundred fifty-four S. aureus isolates were recovered; 208 (59%) were oxacillin (methicillin) susceptible and 146 (41%) were oxacillin resistant (MRSA). On C-MRSA, 139/146 or 95.2% of MRSA isolates were recovered, whereas recovery on TSA II was 86.9% (127/146) (P = 0.0027). The overall specificity of C-MRSA was 99.7%. When C-MRSA was compared to each susceptibility testing method, the sensitivity and specificity, respectively, were as follows: oxacillin MIC by broth microdilution, 94.4% and 96.7%; oxacillin screen agar, 94.3% and 96.7%; PBP2' latex agglutination, 93.7% and 98.5%; cefoxitin disk diffusion, 95.0% and 98.1%; and mecA PCR, 95.1% and 98.1%. In this study, C-MRSA was superior to TSA II for recovery of MRSA from surveillance specimens obtained from the anterior nares and was comparable to conventional, rapid, and molecular susceptibility methods for the identification of MRSA isolates.

Topics: Agar; Anti-Bacterial Agents; Chromogenic Compounds; Cross Infection; Culture Media; Humans; Methicillin; Methicillin Resistance; Nasal Mucosa; Oxacillin; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus; United States

The emergence of heterogeneous populations of methicillin-resistant Staphylococcus aureus (MRSA) causes major problems in routine screening for MRSA. In heterogeneous MRSA populations, a proportion of bacterial cells show low-level resistance to oxacillin, with minimal inhibitory concentrations (MICs) of oxacillin ranging between 1 and 100 mg/l, while in homogeneous MRSA populations, the MIC of oxacillin for all cells is >100 mg/l. Routine oxacillin disk diffusion tests often fail to detect heterogeneous MRSA populations. In the present study, a recently proposed disk diffusion method that employs a cephamycin antibiotic (cefoxitin 30 microg; BD Sensi-disc, Becton Dickinson, Germany) was evaluated using 155 clinical isolates of S. aureus (73 mecA positive and 82 mecA negative). The results were compared with those of other MRSA screening techniques: a disk diffusion test with oxacillin 1 microg and cefoxitin 30 microg (BD Sensi-disc; Becton Dickinson), an MRSA latex agglutination test (Denka Seiken, Japan), and an oxacillin screen agar test (6 microg/ml; Becton Dickinson). Detection of the mecA gene by polymerase chain reaction was considered the gold standard. The performances of the different methods were determined and compared. The results showed that the cefoxitin disk diffusion test is preferable to the oxacillin disk diffusion method for routine screening to detect MRSA.

Topics: Agar; Anti-Bacterial Agents; Cefoxitin; Humans; Methicillin Resistance; Microbial Sensitivity Tests; Oxacillin; Staphylococcal Infections; Staphylococcus aureus

The new chromogenic medium CHROMagar Staph aureus (CASA) was evaluated for its ability to detect and presumptively identify Staphylococcus aureus. Nine hundred forty-two clinical specimens (742 wound, 200 sputum and bronchoalveolar lavage) were cultured on CASA, tryptic soy blood agar (TSBA), and mannitol salt agar (MSA). Of the 153 S. aureus isolates from wounds on any media, 151 grew on CASA and TSBA and 146 on MSA. Sensitivity after 24 hours was 93.5%, 94%, and 77%, respectively, and increased after 48 hours to 99% for CASA and TSBA and to 95% for MSA. Of the 41 isolates recovered from sputum and lavage, all grew on CASA, 27 on TSBA, and 36 on MSA. Sensitivity after 24 hours was 93%, 66%, and 81%, respectively, and 100%, 66%, and 88% after 48 hours. All specimens revealed 99% sensitivity for CASA, 92% for TSBA, and 94% for MSA. Specificity for CASA was 100%. Antimicrobial susceptibility tests showed full agreement between isolates from CASA and from reference media. In conclusion, CASA has a high sensitivity and can identify isolates undetected on conventional media (p value for CASA vs. TSBA was 0.001 and vs. MSA, 0.006). This difference is particularly notable when mixed flora are present. The simplicity of the colony recognition increased the medium specificity, allowing a reliable and rapid method for the detection of S. aureus on the primary plate.

Topics: Agar; Bacterial Typing Techniques; Bacteriological Techniques; Chromogenic Compounds; Colony Count, Microbial; Culture Media; Humans; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

We describe here the development and evaluation of MRSA ID, a new chromogenic agar medium for the specific isolation and identification of methicillin-resistant Staphylococcus aureus (MRSA). We used S. aureus ID (bioMerieux, La Balme Les Grottes, France) and supplemented it with various antimicrobials, including cefoxitin, ciprofloxacin, oxacillin, and methicillin. Cefoxitin proved to be superior to the other antimicrobials for the selection of MRSA from other strains of S. aureus. MRSA ID (consisting of S. aureus ID supplemented with 4 mg of cefoxitin/liter) was evaluated by the use of 747 swabs from various clinical sites. All specimens were also cultured on CHROMagar MRSA and oxacillin resistance screening agar base (ORSAB) and in selective mannitol broth (SMB). A total of 85 MRSA strains were isolated by a combination of all methods. After 22 to 24 h of incubation, 80% of the MRSA strains were isolated as green colonies on MRSA ID, compared with 59 and 62% of the strains that were isolated as colored colonies on CHROMagar MRSA and ORSAB, respectively. After 48 h of incubation, 89, 72, and 78% of the MRSA strains were isolated on MRSA ID, CHROMagar MRSA, and ORSAB, respectively. Sixty-five percent of the strains were isolated by growth in SMB. The specificities of MRSA ID, CHROMagar MRSA, ORSAB, and SMB were 99.5, 99.3, 97.9, and 92.8%, respectively, after 22 to 24 h of incubation. We conclude that MRSA ID is a sensitive and specific medium for the isolation and identification of MRSA.

Topics: Agar; Anti-Bacterial Agents; Chromogenic Compounds; Culture Media; Humans; Methicillin; Methicillin Resistance; Microbial Sensitivity Tests; Staphylococcal Infections; Staphylococcus aureus

S. aureus ID (bioMérieux, La Balme Les Grottes, France) is a new chromogenic agar medium designed to enable the isolation of staphylococci and the specific identification of Staphylococcus aureus. S. aureus produces green colonies on this medium due to production of alpha-glucosidase. To evaluate this medium, a total of 350 wound swabs were cultured onto S. aureus ID, CHROMagar Staph. aureus, and conventional media routinely used in our laboratory. After 18 to 20 h of incubation, 96.8% of strains formed green colonies on S. aureus ID compared with 91.1% of strains forming mauve colonies on CHROMagar Staph. aureus. A total of 94.3% of strains were recovered within 18 to 20 h with conventional media. The sensitivity was increased after 48 h of incubation to 98.7, 96.2, and 95.6% with S. aureus ID, CHROMagar Staph. aureus, and conventional media, respectively. A total of 97.4% of green colonies on S. aureus ID were confirmed as S. aureus compared with 94.4% of mauve colonies on CHROMagar Staph. aureus. We conclude that S. aureus ID is a highly sensitive and specific medium for the isolation and identification of S. aureus from wound swabs.

Topics: Abscess; Agar; Culture Media; False Positive Reactions; Humans; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Bacteriological Techniques; Culture Media; Drug Resistance, Bacterial; Humans; Methicillin Resistance; Oxacillin; Penicillins; Predictive Value of Tests; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

The prevalence of low-level resistance to glycopeptides (teicoplanin MIC > or = 8 microg/mL and vancomycin MIC > or = 4 microg/mL) among staphylococci was investigated over a 15 month period. A total of 2,279 isolates (1,519 S. aureus, 760 coagulase-negative staphylococcus (CNS)) were screened using inoculum of 10(6) CFU/mL and Mueller-Hinton agars supplemented with 8 microg/mL of teicoplanin. Of these, 218 isolates (136 S. aureus and 82 CNS) grew on the screening agar. For these isolates, teicoplanin and vancomycin MICs were determined by agar dilution method and a vancomycin agar screening method was evaluated. The prevalence of low-level resistance to teicoplanin and vancomycin was 7.8% and 0.1% for S. aureus and 8.8% and 0.8% for CNS, respectively. The brain heart infusion agar containing 4 microg/mL of vancomycin failed to detect two out of eight staphylococcal isolates with vancomycin MICs of 4 microg/mL. Furthermore, the method appeared to lack reproducibility. Considering the increasing incidence of vancomycin treatment failure in staphylococcal infection, a more reliable screening method is required.

Topics: Agar; Anti-Bacterial Agents; Drug Resistance, Bacterial; Hospitals, University; Humans; Microbial Sensitivity Tests; Population Surveillance; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus; Teicoplanin; Vancomycin; Vancomycin Resistance

This study evaluated a polymerase chain reaction (PCR) method for detection of methicillin-resistant Staphylococcus aureus (MRSA) in specimens referred for nosocomial surveillance. PCR was used to detect the mecA and nuc gene targets using yellow growth on mannitol salt agar containing 6 mg/liter oxacillin (MSO-6) as a source of DNA (N = 645). The diagnostic values for PCR compared with culture methods were 97% specificity, 100% sensitivity, 96% positive predictive value, and 100% negative predictive value. Total cost for PCR per test is $3.62 compared to $4.77 for culture. However, the total cost per specimen is significantly lower due to only 20% of all surveillance specimens producing yellow colonies on MSO-6. The average turnaround time for the PCR method is 48 h compared with 82 h for culture. PCR amplification of mecA and nuc genes using yellow colonies on MSO-6 is a simple, fast, accurate and cost-effective method for routine use in clinical laboratories for detecting MRSA in surveillance specimens.

Topics: Agar; Bacterial Proteins; Bacteriological Techniques; Carrier Proteins; Cross Infection; Culture Media; Endonucleases; Hexosyltransferases; Humans; Mannitol; Methicillin Resistance; Micrococcal Nuclease; Muramoylpentapeptide Carboxypeptidase; Oxacillin; Penicillin-Binding Proteins; Penicillins; Peptidyl Transferases; Polymerase Chain Reaction; Sensitivity and Specificity; Staphylococcal Infections; Staphylococcus aureus

A total of 414 coagulase-positive staphylococcal strains obtained at the mastitis laboratory, National Veterinary Institute, Uppsala, Sweden, were studied. One hundred and seventy seven strains were used for a frequency study. Ninety-seven per cent were identified as Staphylococcus aureus, 2% as Staphylococcus intermedius and 1% as Staphylococcus hyicus. Two hundred and thirty seven strains with atypical hemolysis reactions on bovine blood agar were randomly selected, with the aim to increase the number of S. intermedius and S. hyicus strains available for testing. Eight different characteristics, including physiological, enzymatical and biochemical properties, were used to identify the coagulase-positive Staphylococcus species. The results of this study suggest that the following tests should be included for correct identification of the 3 different species of coagulase-positive staphylococci: P agar supplemented with acriflavin, beta-galactosidase and hemolytic reaction on chocolate agar. These 3 tests are simple and quick to perform and enable accurate for easy differentiation of the 3 coagulase-positive Staphylococcus species.

Topics: Acriflavine; Agar; Animals; beta-Galactosidase; Cattle; Coagulase; Culture Media; Female; Hemolysis; Mastitis, Bovine; Milk; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

The aim of this study was to develop a simple, reliable, and inexpensive in-house system for routine species identification of staphylococci in clinical practice. The system combines 15 key tests (including carbohydrate fermentation) performed in micro-well strips and antimicrobial disk diffusion susceptibility tests performed on standardised paper disk method antibiotic sensitivity medium agar. Twenty-eight staphylococcal reference strains belonging to 18 different species were correctly identified using this in-house system. A total of 291 clinical staphylococci isolates were evaluated with the in-house system and a conventional identification scheme. The in-house system identified 281 (96.6%) of these 291 isolates. Eleven different species were recognised. The five species most frequently identified were Staphylococcus epidermidis (48.6%), Staphylococcus aureus (27.8%), Staphylococcus haemolyticus (8.2%), Staphylococcus hominis (5.7%), and Staphylococcus warneri (5.3%). There was an agreement of 86.3% between the species identification obtained with the in-house system and the conventional identification scheme. All coagulase-negative isolates initially identified as species other than Staphylococcus epidermidis as well as indistinctly identified isolates were also evaluated with a commercial identification system. The agreement between species identification obtained with the in-house system and the commercial system for 101 identified isolates was 73%. Several isolates that were difficult to distinguish with the conventional scheme and/or the commercial system were identified with the aid of the antimicrobial susceptibility test included in the in-house system. The described test scheme should be of value for identification of clinically significant staphylococci species.

Topics: Agar; Anti-Bacterial Agents; Bacterial Typing Techniques; Carbohydrate Metabolism; Coagulase; Humans; Microbial Sensitivity Tests; Reagent Kits, Diagnostic; Reference Standards; Species Specificity; Staphylococcal Infections; Staphylococcus

We describe a novel mouse model of acute staphylococcal pneumonia induced by intravenous injection of Staphylococcus aureus enmeshed in agar beads. For comparison, we also used various strains of bacteria, including three strains of S. aureus, two strains of Staphylococcus epidermidis, one strain of Streptococcus pyogenes, three strains of Pseudomonas aeruginosa, and one strain of Klebsiella pneumoniae. All except two strains of S. aureus were cleared rapidly from the lungs. When S. aureus NUMR1 enmeshed in agar beads was injected intravenously, the organisms concentrated and remained in the lung for a period longer than several weeks. Multiple lung abscesses were evident macroscopically, and histological examination of the infected lung showed multiple lung abscesses around the pulmonary arterioles, consisting of bacterial colonies encircled with fibrin filaments and surrounded by inflammatory cells of neutrophils and macrophages. When 14 strains of clinically isolated S. aureus were injected intravenously, the number of bacteria recovered from the lung tissue 7 days after infection correlated with the titer of staphylocoagulase (P < 0.01) but not with the titer of clumping factor. Injection of coagulase-deficient mutant strain DU5843 was associated with a markedly reduced number of viable bacteria isolated from the lung, compared with its coagulase-positive parental strain DU5789. Our results suggest that coagulase may play a role in the development of blood-borne staphylococcal pneumonia in our model. Our animal model is simple and reproducible and resembles blood-borne staphylococcal pneumonia in humans, and it could be useful for investigating the pathogenicity or treatment of staphylococcal pulmonary infection, including infections with methicillin-resistant S. aureus.

Topics: Agar; Animals; Bacteremia; Coagulase; Colony Count, Microbial; Disease Models, Animal; Injections, Intravenous; Lung; Male; Mice; Mice, Inbred Strains; Microspheres; Pneumonia, Staphylococcal; Staphylococcal Infections; Staphylococcus aureus

Staphylococcus aureus isolates from human clinical sources were incubated for various times in modified 110 medium and tested for production of capsule by the serum-soft agar technique. Ten (5.7%) of 175 isolates were encapsulated after incubation for 24 h. A more detailed examination of 77 isolates showed that incubation period affected the production of capsule. After 2 h, 31% were encapsulated, but after 6 h and 24 h this decreased to 17% and 4% respectively. Rapid passage in vitro induced the expression of capsule in four of 50 unencapsulated strains. Only three of 20 encapsulated strains could be typed with standard antisera.

Topics: Agar; Culture Media; Humans; Polysaccharides, Bacterial; Serotyping; Staphylococcal Infections; Staphylococcus aureus

Besides the two well-known blood-clotting substances, coagulase and clumping factor, a third one has been identified from the staphylococci which is a cell surface polysaccharide, is alkali stable, and induces compact-colony formation in serum soft agar. Using some 97 clinical strains of Staphylococcus aureus, we found that in production and activity the substances were distinctly different.

Topics: Agar; Coagulase; Fibrinogen; Humans; Polysaccharides, Bacterial; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Animals; Blood; Caseins; Cattle; Culture Media; Folliculitis; Furunculosis; Humans; Microscopy, Electron; Rabbits; Staphylococcal Infections; Staphylococcus

Using the serum-soft agar technic of Staphylococcus epidermidis typing, an epidemiologic study of pollution with S. epidermidis in the tuberculosis and pediatric wards of a hospital was conducted. Specimen samples were taken from 334 locations, including beds, bedspreads, pillows, doors and window knobs, chairs, tables, and incubators of premature infants. These were cultured on Staphylococcus 110 medium and the strains identified as S. epidermidis were obtained. Of the strains from both patients' rooms and the nurses' station in the tuberculosis ward a considerable number were of serotype 53, suggesting an interrelationship of this organism and these locations. In the rooms of newborns and premature infants in the pediatric ward, 55.5% of the strains of S. epidermidis isolated were of the serotype 53/408, indicating a high degree of pollution of these environments with these serotype strains.

Topics: Agar; Animals; Child, Preschool; Equipment Contamination; Humans; Infant, Newborn; Serotyping; Serum; Staphylococcal Infections; Staphylococcus epidermidis; Tuberculosis

Modifications of the staphylococcal counterimmunoelectrophoresis technique were evaluated to determine how variations in the procedure affected results. Neither a buffer pH range of 7.8 to 9.0 nor buffer molarity of 0.015 or 0.025 when tested in combinations caused appreciable differences. However, use of different agar preparations or delay in addition of antigen to the test slide altered the location of the precipitin band. Agarose was found to be more sensitive in determining the serum precipitin titer and provided a better photographic record than either Ionagar or Noble agar.

Topics: Agar; Antibodies, Bacterial; Counterimmunoelectrophoresis; Diagnosis, Differential; Evaluation Studies as Topic; Humans; Hydrogen-Ion Concentration; Immunoelectrophoresis; Osmolar Concentration; Sepharose; Staphylococcal Infections; Staphylococcus aureus; Teichoic Acids

Topics: Agar; Animals; Antibodies, Bacterial; Blood Bactericidal Activity; Culture Media; Erythrocytes; Hemolysin Proteins; Hemolysis; Humans; Immunodiffusion; Methods; Rabbits; Staphylococcal Infections; Staphylococcal Toxoid; Staphylococcus

Topics: Administration, Oral; Agar; Animals; Bacillus subtilis; Bacteria; Chemical Phenomena; Chemistry; Dicloxacillin; Dogs; Drug Stability; Hydrogen-Ion Concentration; Immunodiffusion; Injections, Intravenous; Mice; Oxacillin; Penicillin G; Penicillin Resistance; Penicillinase; Penicillins; Pyrazoles; Staphylococcal Infections; Staphylococcus; Streptococcal Infections; Streptococcus pyogenes

Topics: Agar; Animals; Carbohydrate Metabolism; Cell Fractionation; Cytoplasm; Disease Models, Animal; Fatty Acids; Lethal Dose 50; Lipid Metabolism; Male; Mice; Nafcillin; Nitrogen; Organ Specificity; Oxidative Phosphorylation; Oxygen Consumption; Proteins; Staphylococcal Infections; Staphylococcus; Toxins, Biological

Topics: Agar; Anti-Bacterial Agents; Cephalosporins; Culture Techniques; Germany, West; Humans; Microbial Sensitivity Tests; Nitrofurantoin; Penicillin Resistance; Penicillins; Staphylococcal Infections; Staphylococcus; Streptomycin; Sulfamethoxazole; Tetracycline

Topics: Agar; Anti-Bacterial Agents; Culture Media; Hospitals; Humans; Methods; Microbial Sensitivity Tests; Staphylococcal Infections; United Kingdom; Urinary Tract Infections

Topics: Administration, Oral; Adolescent; Adult; Agar; Aged; Candidiasis; Cephalosporins; Escherichia coli; Escherichia coli Infections; Female; Haemophilus Infections; Haemophilus influenzae; Humans; Klebsiella; Klebsiella Infections; Male; Microbial Sensitivity Tests; Middle Aged; Nausea; Proteus; Proteus Infections; Staphylococcal Infections; Streptococcal Infections; Streptococcus; Streptococcus pneumoniae; Streptococcus pyogenes; Urinary Tract Infections; Vulvovaginitis

A total of 350 staphylococci isolated from various clinical sources were examined for bound and free coagulase, fermentation of mannitol, and deoxyribonuclease. The economical coagulase-mannitol-agar method of Esber and Faulcomer was found to be suitable for the detection of free coagulase and mannitol fermentation. A significant number of coagulase- and mannitol-negative staphylococci proved to be deoxyribonuclease-positive.

Topics: Agar; Animals; Bacteriological Techniques; Blood; Coagulase; Deoxyribonucleases; Humans; Mannitol; Sheep; Staphylococcal Infections; Staphylococcus

Topics: Agar; Bacteriological Techniques; Humans; Iodine; Methods; Nasal Mucosa; Penicillin G; Penicillinase; Staphylococcal Infections; Staphylococcus; Starch; Time Factors

The cellophane-over-agar technique has been shown to give high titers of enterotoxins A, B, and C for routine testing of staphylococci for enterotoxigenicity.

Topics: Agar; Animals; Brain; Caseins; Cattle; Cellophane; Culture Media; Enterotoxins; Female; Heart; Humans; Immunodiffusion; Mastitis, Bovine; Methicillin; Microbial Sensitivity Tests; New Zealand; Penicillin Resistance; Staphylococcal Infections; Staphylococcus

Topics: Adolescent; Adult; Agar; Cephalosporins; Child; Drug Resistance, Microbial; Electrolytes; Female; Humans; Liver; Male; Middle Aged; Otitis Externa; Otitis Media; Staphylococcal Infections; Staphylococcus; Streptococcal Infections; Tonsillitis

Topics: Agar; Bronchi; Bronchial Diseases; Chromatography; Cystic Fibrosis; Humans; Phenylacetates; Respiratory Tract Infections; Sputum; Staphylococcal Infections; Staphylococcus

Some strains of Staphylococcus aureus grew as compact colonies in Brain Heart Infusion-serum-soft agar but as diffuse colonies in a modified Staphylococcus 110-serum-soft agar. These strains were designated "pseudocompact." Strains showing compact-type colonial morphology in both media were designated "compact," whereas strains showing diffuse-type growth in both media were designated "diffuse." It was observed that the most recently isolated strains of S. aureus were of the pseudocompact type, whereas most stock culture strains tested were of the compact type. Using cultures recently isolated from clinical material, it was shown that pseudocompact strains convert to compact-type growth after prolonged incubation. Interconversion of compact, diffuse, and pseudocompact growth forms could be induced in vitro by appropriate cultural conditions, and conversion of growth type was also observed in vivo. Femoral abscesses produced in mice by four different compact-type strains showed conversion to diffuse or pseudocompact-type growth during the course of the infection.

Topics: Abscess; Agar; Animals; Bacteriological Techniques; Blood; Brain; Culture Media; Culture Techniques; Mice; Staphylococcal Infections; Staphylococcus

Topics: Agar; Animals; Anti-Bacterial Agents; Coagulase; Drug Resistance, Microbial; Erythrocytes; Hemolysin Proteins; Humans; Hyaluronoglucosaminidase; Mannitol; Pigments, Biological; Rabbits; Sheep; Staphylococcal Infections; Staphylococcus

Topics: Agar; Animals; Humans; Indicators and Reagents; Mannitol; Nasopharyngeal Diseases; Staphylococcal Infections; Staphylococcus

Topics: Agar; Antigens; Chemical Precipitation; Child; Culture Media; Humans; Staphylococcal Infections; Staphylococcal Toxoid; Staphylococcus

Topics: Agar; Anti-Bacterial Agents; Exudates and Transudates; Granulation Tissue; Humans; Staphylococcal Infections; Wound Healing; Wound Infection

Topics: Agar; Animals; Anti-Infective Agents, Local; Culture Media; Research; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Davis, Nour A. (University of Lagos Medical School, Lagos, Nigeria), and G. H. G. Davis. Ecology of nasal staphylococci. J. Bacteriol. 89:1163-1168. 1965.-The rate of nasal carriage of Staphylococcus aureus in Nigerian adults (46%) approximates that found in other countries. The rate in infants under 12 months was ca. 70%, which exceeds that found elsewhere, e.g., England. The incidence of penicillin resistance in nasal staphylococci (50 to 60%) is about the same as has been found in strains isolated from infections in outpatients in urban centers in this country. Mannitol-polymyxin agar was used for the selection and differentiation of coagulase-positive staphylococci and proved to be valuable in such studies. Our results clearly show that the degree of colonization by S. aureus significantly influences, or is influenced by, the rate of incidence of other bacteria in the vestibular flora, particularly in the case of diphtheroids and coagulase-negative cocci. The relationship between the degree of nasal microbial colonization and social and other factors is discussed.

Topics: Adult; Agar; Anti-Bacterial Agents; Carrier State; Child; Coagulase; Cross Infection; Culture Media; Drug Resistance; Drug Resistance, Microbial; Humans; Infant; Mannitol; Medical Staff, Hospital; Nigeria; Nose; Penicillins; Polymyxins; Research; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Topics: Agar; Clinical Laboratory Techniques; Coagulase; Humans; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Agglutination; Complement Factor H; Research; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Topics: Adhesives; Agar; Anti-Infective Agents; Cellophane; Cellulose; Pharmacology; Research; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus; Thiram

Topics: Agar; Antistreptolysin; Aortic Valve Stenosis; Arthritis; Dextran Sulfate; Dextrans; Glomerulonephritis; Humans; Immune Sera; Mitral Valve Stenosis; Osteomyelitis; Rheumatic Fever; Staphylococcal Infections; Streptococcal Infections; Tonsillitis

Beining, Paul R. (The Catholic University of America, Washington, D.C.) and E. R. Kennedy. Characteristics of a strain of Staphylococcus aureus grown in vivo and in vitro. J. Bacteriol. 85:732-741. 1963.-A comparative survey was conducted on the characteristics of a strain of Staphylococcus aureus after it had been grown in vitro (VSB) and after it had been collected from the peritoneal exudate of an infected guinea pig (GSB). Both VSB and GSB strains gave the same results when studied in an extensive series of tests, including bound and soluble coagulases, bacteriophage type, antibiotic-sensitivity pattern, the usual fermentation reactions, deoxyribonucleic acid base composition, and qualitative tests for hemolysins, deoxyribonuclease, ribonuclease, staphylokinase, staphyloprotease, lipase, and phosphatase. The in vivo strain differed significantly from the in vitro strain in respiratory rate, agar gel diffusion studies, agglutinability in tube tests, virulence tests in rabbits and mice, growth on tellurite-glycine agar, susceptibility to human gamma-globulin in agar, and in the quantitative production of deoxyribonuclease, alpha-hemolysin, leucocidin, and hyaluronidase.

Topics: Agar; Animals; Coagulase; Culture Media; Guinea Pigs; Hemolysin Proteins; In Vitro Techniques; Mice; Rabbits; Research; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus; Virulence

The numbers of Staphylococcus aureus 196E surviving heat treatment in milk for various times at 60 C were determined by plate count with normal and modified Staphylococcus Medium No. 110 (S-110), with Plate Count Agar (PCA), and by milk enrichment techniques. Portions of specific heated samples appeared to contain lower populations of S. aureus 196E when the survivors were enumerated with normal S-110 than with PCA. Similarly, the times at 60 C needed for total destruction of the culture suspension in the test milk appeared to be shorter when survival was determined with normal S-110 agar. The apparently lower thermal death times were found to be related to the NaCl content of the S-110 medium, because use of S-110 agar containing lesser concentrations of NaCl resulted in growth of larger numbers of heat-shocked S. aureus 196E.

Topics: Agar; Animals; Culture Media; Dairy Products; Heat Exhaustion; Hot Temperature; Milk; Research; Sodium Chloride; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Cetin, E. T. (Istanbul University, Istanbul, Turkey). Hemolysin-inhibiting substance in Staphylococcus aureus strains. J. Bacteriol. 86:407-413. 1963.-Of 144 Staphylococcus aureus strains isolated from pathological specimens, 3.4% did not cause hemolysis on sheep blood agar; the remainder produced hemolytic and semihemolytic zones, most of which were surrounded by a dense red band. Most of the strains causing pronounced hemolysis and a large dense red band on sheep blood agar also produced a dense red band on human blood agar after incubation at 37 C for about 1 week. In the dense red band on human blood agar, circles of hemolysis were observed when petri dishes were kept at room temperature for approximately 1 more week. The dense red band inhibited delta hemolysis of some of the S. aureus strains growing nearby. Certain strains failing to produce the dense red band on human blood agar inhibited delta hemolysis of other strains grown near them. A hemolysis-inhibiting substance (HIS) was produced in broth and agar media, and could be extracted from agar cultures. HIS was stable for 1 hr at 56 C and for 15 min at 100 C. It lost 75% of its effect when heated for 30 min at 100 C and became ineffective when heated at the same temperature for 45 min. Conditioned hemolysis occurred when some saprophytic gram-positive bacteria grew near or within the dense red band. These organisms also produced conditioned hemolysis without the presence of a visible dense red band, when growing near the strains inhibiting delta hemolysis. When such strains were grown on human blood agar, a conditioned hemolysis also occurred after the border of the medium was flamed.

Topics: Agar; Animals; Cell Death; Culture Media; Hemolysin Proteins; Hemolysis; Hot Temperature; Humans; Research; Sheep; Sprains and Strains; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Mossel, D. A. A. (Central Institute for Nutrition and Food Research T.N.O., Utrecht, The Nethrlands). Attempt in classification of catalase-positive staphylococci and micrococci. J. Bacteriol. 84:1140-1147. 1962.-About 390 strains of Staphylococcus aureus, isolated from clinical material, and about 190 strains of coagulase-negative staphylococci and micrococci from strictly nonclinical habitats were studied by the following recently recommended biochemical tests: anaerobic dissimilation ("fermentation") of mannitol, gelatin liquefaction, type of growth on tellurite-glycine agar, hydrolysis of urea, and KCN tolerance. The latter three tests appeared either not specific for, or not positive for, most S. aureus strains. Virtually all strains of S. aureus were gelatin-positive, but 71% of the other types of cocci also liquefied gelatin. Rapid anaerobic breakdown of mannitol, however, was shown by ca. 95% of the strains of S. aureus, and late fermentation by an additional 3%. Of 105 obligately aerobic coagulase tive cocci (micrococci), none fermented mannitol; of 40 facultatively anaerobic, coagulase-negative cocci (staphylococci), only 7 (18%) fermented mannitol. Oxidative metabolism of mannitol occurred in only three (<1%) strains of S. aureus but was detected in roughly half of the isolates of both groups of coagulase-negative cocci. Pigmentation was confirmed to be of little value, because roughly 50% of both coagulase-positive and -negative strains showed a pale-yellow color on Chapman's mannitol salt agar while 13% of the S. aureus strains tested were white. A key to the classification of catalase-positive cocci consistent with that currently used for Enterobacteriaceae has been based on these figures.

Topics: Agar; Catalase; Coagulase; Fermentation; Humans; Mannitol; Micrococcus; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Topics: Agar; Biological Phenomena; Humans; Physiological Phenomena; Staphylococcal Infections; Staphylococcus; Staphylococcus aureus

Topics: Agar; Emotions; Micrococcus; Staphylococcal Infections; Staphylococcus aureus

Topics: Agar; Animals; Mucoproteins; N-Acetylmuramoyl-L-alanine Amidase; Rabbits; Sheep; Sheep, Domestic; Staphylococcal Infections; Staphylococcus

Topics: Agar; Coagulase; Humans; Staphylococcal Infections; Staphylococcus