agar and triphenyltetrazolium

Accurate enumeration of Paenibacillus mucilaginosus (formerly Bacillus mucilaginosus) bacterium from environmental samples on solid medium is challenging owing to its extensive extracellular polysaccharides (EPS) excretion. In the present study, P. mucilaginosus enumeration has been facilitated by a simple modification: addition of triphenyl tetrazolium chloride (TTC) to growth medium and application of a second soft agar layer. Results show distinctively better and accurate colonies' count. This method can be applied to all bacterial species that produce excessive EPS that may interfere with direct count.

Topics: Agar; Colony Count, Microbial; Coloring Agents; Culture Media; Paenibacillus; Polysaccharides; Tetrazolium Salts

Agar diffusion method has been used to evaluate antimicrobial activity since the discovery of penicillin. Nevertheless, little progress has occurred in reducing the time required to determine growth inhibition zones. The aim of this work was to develop, optimize and validate rapid microbiological methods (RMMs) for cephalosporin antibiotics using triphenyltetrazolium chloride (TTC) to reduce the incubation time of the assays. Through a factorial design in which the inoculum suspension, incubation time, and percentage of the TTC solution were varied, it was possible to validate the RMMs for cefazolin, cefuroxime, ceftriaxone, and cefepime. The validated conditions employed 5 mL of MHA medium inoculated with 2% of Staphylococcus aureus suspension, incubation time of 5 h and 30 min at 37 ± 1 °C and the addition of 0.3% TTC solution in 1% agar, cefazolin and cefuroxime in concentrations from 15 to 60 µg mL

Topics: Agar; Anti-Bacterial Agents; Cephalosporins; Diffusion; Dose-Response Relationship, Drug; Microbial Sensitivity Tests; Staphylococcus aureus; Structure-Activity Relationship; Tetrazolium Salts

Candida dubliniensis, an emerging oral pathogen, phenotypically resembles Candida albicans so closely that it is easily misidentified as such. The aim of the present study was to evaluate the usefulness of two phenotypic methods, growth at 45 degrees C and 2,3,5-triphenyltetrazolium chloride (TTC) reduction, for confirming presumptive identification of C. dubliniensis and C. albicans by colony color on CHROMagar Candida (CAC) medium. A combination of these methods was used to establish the prevalence of oral C. dubliniensis in an Italian population of 45 human immunodeficiency virus (HIV)-infected subjects. Twenty-two samples (48.9%) were positive for yeasts on CAC medium producing a total of 37 fungal isolates. The colony color and 45 degrees C growth ability test correctly identified all C. dubliniensis and C. albicans isolates (5/37, 13.5%, and 16/37, 43.2%, respectively), while assessment of TTC reduction misidentified one C. albicans isolate. The isolation rate of C. dubliniensis was 11.1% (5/45 patients). All of the C. dubliniensis isolates were highly susceptible to fluconazole (MIC = 0.5 microg/ml). The combination of CAC medium screening with growth at 45 degrees C and TTC reduction tests may represent a simple, reliable and inexpensive identification protocol for C. dubliniensis.

Topics: Adult; Agar; Antifungal Agents; Candida; Candida albicans; Candidiasis, Oral; Chromogenic Compounds; Colony Count, Microbial; Coloring Agents; Culture Media; DNA, Fungal; Drug Resistance, Fungal; Female; Fluconazole; HIV Infections; Humans; Italy; Male; Middle Aged; Mouth; Phenotype; Polymerase Chain Reaction; Temperature; Tetrazolium Salts

Direct plating is an effective technique for isolation and enumeration of Campylobacters from a variety of sample types; however, distinguishing Campylobacters from non-Campylobacter contaminants that frequently grow on many existing agars is difficult. In this study, it was determined that exposing Campylobacters to low levels (200 mg/liter) of triphenyltetrazolium chloride (TTC) was not inhibitory to growth yet was sufficient to give a deep-red to magenta color to the colonies. The new agars (Campy-Line agar [CLAI and Campy-Line blood agar [CLBA]) are translucent. The contrast of deep-red colonies on a translucent background greatly facilitates Campylobacter isolation and makes enumeration on light boxes or by electronic means possible. Direct plating of broiler carcass rinse samples (n = 20) was compared on Campy-Cefex agar and CLA. Recovery of Campylobacter populations was not significantly different between the agars (P < 0.05); however, enumeration was much less labor intensive with the CLA. No contaminants were observed on the CLA, whereas the Cefex agar supported the growth of approximately 14 contaminating (non-Campylobacter) CFU/ml. In a separate trial, recovery of Campylobacters from carcass rinses (n = 25) was similarly compared on Cefex, CLA, and CLBA. Again, recovery of Campylobacters was not significantly different between the agars (Pearson correlation coefficient = 0.988), whereas about nine contaminating (non-Campylobacter) CFU/ml were observed on Cefex agar and none on CLA or CLBA. Although some contaminants can still grow on CLA and CLBA and can present red colonies, most of these contaminants are easily distinguished from Campylobacter by differences in colony morphology.

Topics: Agar; Animals; Campylobacter; Chickens; Colony Count, Microbial; Coloring Agents; Culture Media; Tetrazolium Salts

A new method of Candida subspecies discrimination on Sabouraud-triphenyltetrazolium agar is reported. Five hundred sixty-two strains of Candida and Torulopsis glabrata, previously identified by conventional mycological methods, were studied. Each strain received a three-letter code and a number based on its colonial morphology. Sixteen morphotypes were found for Candida albicans, 6 were found for Candida parapsilosis, 4 were found for both Candida guilliermondii and Candida krusei, and 12 were found for Candida tropicalis. None of the 56 T. glabrata strains studied grew on this agar. A reproducibility of 95% was found for C. albicans. The simplicity and low cost could make this method useful for typing Candida spp.

Topics: Agar; Candida; Mycological Typing Techniques; Reproducibility of Results; Tetrazolium Salts

An improved tetrazolium agar medium for testing sugar fermentation in lactobacilli is described. Basal medium 86 was essentially a modified MRS broth with the omission of glucose. The standard formula was 30 micrograms/ml of 2,3,5-triphenyltetrazolium chloride, 2% sugar to be tested, and 2% agar in medium 86. Plates were incubated anaerobically for 2 days at 37C or 5 days at 30C, depending on the strain. With three strains each of group II and III lactobacilli, colorless, fermentation-positive colonies were clearly differentiated from red, fermentation-negative colonies. For three strains of group I lactobacilli, this medium was not satisfactory because they grew poorly on it unless supplemented with a sugar.

Topics: Agar; Carbohydrate Metabolism; Culture Media; Fermentation; Lactobacillus; Tetrazolium Salts

Topics: Agar; Culture Media; Drinking Water; Fatty Alcohols; Tetrazolium Salts; Water Microbiology; Water Supply

Topics: Agar; Animals; Bacteriology; Breast; Dairy Products; Escherichia coli; Gram-Negative Bacteria; Ice Cream; Lactose; Milk; Tetrazolium Salts; Water; Water Supply

Topics: Agar; Enterobacter aerogenes; Escherichia coli; Fatty Alcohols; Poloxalene; Tetrazolium Salts