cefotaxime and Salmonella-Infections--Animal

The antimicrobial resistance of Salmonella strains is rapidly increasing worldwide, which poses significant threats to animal and public health. In this study, a total of 249 porcine Salmonella isolates collected in China during 2008-2015 were examined, including 155 clinical isolates from diseased pigs and 94 nonclinical isolates from healthy pigs. Based on the minimum inhibitory concentration of seven antimicrobial agents, 96.4% of the isolates were resistant to at least one of the tested antibiotics and 81.0% of them showed multidrug resistance. The highest antimicrobial resistance was observed for tetracycline (85.9%), and the lowest was found for cefotaxime (13.3%). The isolates from diseased pigs exhibited significantly higher levels of antimicrobial resistance than those from healthy pigs. Twenty-two isolates from healthy pigs were resistant to ciprofloxacin, which may inhibit the curative effectiveness of fluoroquinolones on bacterial food-borne poisoning and infections in humans caused by contaminated food. Moreover, cefotaxime resistance of the strains isolated from diseased pigs during 2013-2015 was significantly higher compared with the strains isolated during 2008-2010. Further study showed that the correlation between phenotypic and genotypic resistance varied among the isolates from different sources, and in many cases, the presence of resistance genes was not consistent with the resistance to the corresponding antimicrobials. These results are very significant for veterinary practice and public health.

Topics: Animal Husbandry; Animals; Anti-Bacterial Agents; Cefotaxime; China; Ciprofloxacin; Drug Resistance, Multiple, Bacterial; Farms; Genotype; Phenotype; Salmonella; Salmonella Infections, Animal; Serogroup; Swine; Swine Diseases; Tetracycline

Salmonellosis is a major global foodborne infection, and strains that are resistant to a great variety of antibiotics have become a major public health concern. The aim of this study was to identify genes conferring resistance to fluoroquinolones and extended-spectrum β-lactams in nontyphoidal Salmonella (NTS) from patients and food-producing animals in China. In total, 133 and 21 NTS isolates from animals and humans, respectively, exhibiting concurrent resistance to ciprofloxacin and cefotaxime were cultured independently from 2009 to ∼2013. All of the isolates were identified, serotyped, and subjected to antimicrobial susceptibility testing. Importantly, the isolates with concurrent resistance to ciprofloxacin and cefotaxime all were confirmed as S. enterica serovar Indiana. The presence of fluoroquinolone resistance genes and extended-spectrum β-lactamases (ESBLs) was established by PCR and DNA sequencing. The occurrence and diversity of different genes conferring fluoroquinolone resistance [qepA, oqxAB, and aac(6')-Ib-cr] with mutations in topoisomerase-encoding genes (gyrA and parC) and several ESBLs (including CTX-M-65, CTX-M-27, CTX-M-15, CTX-M-14, and CTX-M-14/CTX-M-15) were noteworthy. Genes located on mobile genetic elements were identified by conjugation and transformation. Pulsed-field gel electrophoresis, used to determine the genetic relationships between these isolates, generated 91 pulsotypes from 133 chicken isolates and 17 pulsotypes from the 21 clinical isolates that showed considerable diversity. Analysis of the pulsotypes obtained with the isolates showed some clones appeared to have existed for several years and had been disseminating between humans and food-producing animals. This study highlights the emergence of ciprofloxacin- and cefotaxime-resistant S. enterica serovar Indiana, posing a threat to public health.

Topics: Animals; Anti-Bacterial Agents; beta-Lactamases; Cefotaxime; China; Ciprofloxacin; DNA Topoisomerases; DNA, Bacterial; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Feces; Fluoroquinolones; Genotype; Humans; Microbial Sensitivity Tests; Salmonella; Salmonella enterica; Salmonella Infections, Animal

It has been proposed that sub-inhibitory concentrations of antibiotics play a role in virulence modulation. In this study, we evaluated the ability of Salmonella enterica serovar Typhimurium (hereafter S. Typhimurium) to colonize systemically BALB/c mice after exposure to a sub-inhibitory concentration of cefotaxime (CTX). In vivo competition assays showed a fivefold increase in systemic colonization of CTX-exposed bacteria when compared to untreated bacteria. To identify the molecular mechanisms involved in this phenomenon, we carried out a high-throughput genetic screen. A transposon library of S. Typhimurium mutants was subjected to negative selection in the presence of a sub-inhibitory concentration of CTX and genes related to anaerobic metabolism, biosynthesis of purines, pyrimidines, amino acids and other metabolites were identified as needed to survive in this condition. In addition, an impaired ability for oxygen consumption was observed when bacteria were cultured in the presence of a sub-inhibitory concentration of CTX. Altogether, our data indicate that exposure to sub-lethal concentrations of CTX increases the systemic colonization of S. Typhimurium in BALB/c mice in part by the establishment of a fitness alteration conducive to anaerobic metabolism.

Topics: Anaerobiosis; Animals; Anti-Bacterial Agents; Bacterial Load; Cefotaxime; Female; Gene Expression Regulation, Bacterial; Mice; Mice, Inbred BALB C; Oxygen; Salmonella Infections, Animal; Salmonella typhimurium; Virulence

To identify the mechanism(s) underlying cefotaxime resistance in 118 of 21,641 (0.55%) non-typhoidal Salmonella enterica isolates collected from humans throughout England and Wales from January 2010 to September 2012.. Non-duplicate isolates (n = 118) resistant to cefotaxime (MICs >1 mg/L) were screened by PCR for genes encoding CTX-M extended-spectrum β-lactamases (ESBLs) and associated ISEcp1-like elements, and for genes encoding acquired AmpC, SHV, TEM, VEB, PER and GES β-lactamases. Sequencing was used to identify specific alleles in selected isolates. Carbapenem resistance was sought by ertapenem disc screening.. Seventy-nine isolates (0.37% of all referred S. enterica) produced ESBLs, 37 isolates (0.17%) produced CMY-type AmpC enzymes, and 1 isolate had both enzyme types; the mechanism of cefotaxime resistance in 3 isolates could not be identified. Group 1 CTX-M genes were identified in 57 isolates belonging to 22 serotypes, with CTX-M-1 (n = 11), -15 (n = 9) and -55/57 (n = 8) the most prevalent alleles among the 29 (51%) investigated. CTX-M-2 (n = 5), -14 (n = 5), -8 (n = 1) and -65 (n = 1) were also identified. TEM-52 was identified in two isolates and SHV-12 in seven isolates. There was no evidence of carbapenem resistance. ESBL and AmpC genes were detected in both domestically acquired and travel-associated salmonellae. Eighty-nine isolates (75%) were multidrug resistant (resistant to at least three antimicrobial classes) and 42 (36%) had decreased susceptibility to ciprofloxacin (MICs 0.25-1 mg/L), with a further 13 (11%) isolates resistant (MICs >1 mg/L).. The prevalence of CTX-M and acquired AmpC genes in human non-typhoidal S. enterica from England and Wales is still low, but has increased from 0.03% in 2001-03 to 0.49% in 2010-12. Resistance to third-generation cephalosporins requires monitoring as it may reduce therapeutic options.

Topics: Alleles; Animals; Anti-Bacterial Agents; Bacterial Proteins; beta-Lactam Resistance; beta-Lactamases; Cefotaxime; Cephalosporins; DNA, Bacterial; England; Humans; Microbial Sensitivity Tests; Prevalence; Salmonella enterica; Salmonella Infections; Salmonella Infections, Animal; Sequence Analysis, DNA; Wales

In 2009, CTX-M Enterobacteriaceae and Salmonella isolates were recovered from a UK pig farm, prompting studies into the dissemination of the resistance and to establish any relationships between the isolates.. PFGE was used to elucidate clonal relationships between isolates whilst plasmid profiling, restriction analysis, sequencing and PCR were used to characterize the CTX-M-harbouring plasmids.. Escherichia coli, Klebsiella pneumoniae and Salmonella 4,5,12:i:- and Bovismorbificans resistant to cefotaxime (n = 65) were recovered and 63 were shown by PCR to harbour a group 1 CTX-M gene. The harbouring hosts were diverse, but the group 1 CTX-M plasmids were common. Three sequenced CTX-M plasmids from E. coli, K. pneumoniae and Salmonella enterica serotype 4,5,12:i:- were identical except for seven mutations and highly similar to IncI1 plasmid ColIb-P9. Two antimicrobial resistance regions were identified: one inserted upstream of yacABC harbouring ISCR2 transposases, sul2 and floR; and the other inserted within shfB of the pilV shufflon harbouring the ISEcp1 transposase followed by blaCTX-M-1.. These data suggest that an ST108 IncI1 plasmid encoding a blaCTX-M-1 gene had disseminated across multiple genera on this farm, an example of horizontal gene transfer of the blaCTX-M-1 gene.

Topics: Animals; Anti-Bacterial Agents; Base Sequence; beta-Lactamases; Cefotaxime; Drug Resistance, Multiple, Bacterial; Escherichia coli; Escherichia coli Infections; Gene Transfer, Horizontal; Klebsiella Infections; Klebsiella pneumoniae; Microbial Sensitivity Tests; Mutation; Plasmids; Salmonella enterica; Salmonella Infections, Animal; Sequence Analysis, DNA; Swine; United Kingdom

Frequent and indiscriminate use of existing battery of antibiotics has led to the development of multi drug resistant (MDR) strains of pathogens. As decreasing the concentration of the antibiotic required to treat Salmonellosis might help in combating the development of resistant strains, the present study was designed to assess the synergistic effects, if any, of nisin, in combination with conventional anti-Salmonella antibiotics against Salmonella enterica serovar Typhimurium. Minimum inhibitory concentrations (MICs) of the selected antimicrobial agents were determined by micro and macro broth dilution assays. In-vitro synergy between the agents was evaluated by radial diffusion assay, fractional inhibitory concentration (FIC) index (checkerboard test) and time-kill assay. Scanning electron microscopy (SEM) was also performed to substantiate the effect of the combinations. In-vivo synergistic efficacy of the combinations selected on the basis of in-vitro results was also evaluated in the murine model, in terms of reduction in the number of Salmonellae in liver, spleen and intestine. Nisin-ampicillin and nisin-EDTA combinations were observed to have additive effects, whereas the combinations of nisin-ceftriaxone and nisin-cefotaxime were found to be highly synergistic against serovar Typhimurium as evident by checkerboard test and time-kill assay. SEM results revealed marked changes on the outer membrane of the bacterial cells treated with various combinations. In-vivo synergy was evident from the larger log unit decreases in all the target organs of mice treated with the combinations than in those treated with drugs alone. This study thus highlights that nisin has the potential to act in conjunction with conventional antibiotics at much lower MICs. These observations seem to be significant, as reducing the therapeutic concentrations of antibiotics may be a valuable strategy for avoiding/reducing the development of emerging antibiotic resistance. Value added potential of nisin in the efficacy of conventional antibiotics may thus be exploited not only against Salmonella but against other Gram-negative infections as well.

Topics: Ampicillin; Animals; Anti-Bacterial Agents; Cefotaxime; Ceftriaxone; Drug Synergism; Drug Therapy, Combination; Edetic Acid; Female; Intestines; Liver; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Nisin; Salmonella Infections, Animal; Salmonella typhimurium; Spleen; Survival Analysis; Time Factors; Treatment Outcome

The efficacies of various antibiotics were compared in Salmonella typhimurium infection in mice. Treatment began 24 h after challenge. Antibiotics were given subcutaneously every 12 or 24 h in the following daily doses: 200 mg/kg for ampicillin, 100 mg/kg for chloramphenicol, cefotaxime and ceftriaxone, 50 mg/kg for pefloxacin. The number of bacteria in the spleens was determined after 3 and 7 days of treatment. In animals treated with ceftriaxone or pefloxacin the mean number of bacteria per spleen was from one to two log10 lower than in animals treated with other antibiotics. Similar results were obtained in genetically susceptible or resistant mice. The MIC being similar for cefotaxime, ceftriaxone and pefloxacin, the better in vivo activity of the two latter drugs appears to be related to their pharmacokinetic properties.

Topics: Ampicillin; Animals; Anti-Bacterial Agents; Cefotaxime; Ceftriaxone; Chloramphenicol; Female; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Norfloxacin; Pefloxacin; Salmonella Infections, Animal; Salmonella typhimurium

Six clinical isolates and 1 reference strain of Salmonella typhimurium were sensitive to conventional antibiotics (ampicillin, chloramphenicol, cotrimoxazole), cefotaxime (CTX), and fosfomycin ( FOSFO ). All 7 strains carried a 55 megadalton plasmid ( Birnboim - Doly agarose gel electrophoresis technique) and were of comparable virulence for outbred NMRI mice (LD50 values = range of 1.7 X 10(5)-1.0 X 10(6) CFU; intraperitoneal route). CTX (5 mg/25 g mouse/day, divided into 2 doses; duration = 7 days) proved efficacious against 3 selected strains (No. H 8800, 14, and 20) of S. typhimurium (p less than 0.01). FOSFO (same therapeutic regimen) failed in this regard; following transitory improvement of diseased animals (days 2-4), the mortality of treated animals eventually approached that of untreated control animals. Administration of 15 mg FOSFO /mouse/day likewise failed to enhance murine survival. Reisolated S. typhimurium bacteria of these 3 assay strains still were susceptible to FOSFO . In vitro, CTX likewise surpassed FOSFO in bactericidal activity against the same 3 S. typhimurium strains on a weight-for-weight basis in various biological fluids (human midstream urine; human defibrinated blood; murine thioglycolate-induced macrophage-rich peritoneal exudate).

Topics: Animals; Anti-Bacterial Agents; Cefotaxime; Drug Resistance, Microbial; Female; Fosfomycin; Male; Mice; Microbial Sensitivity Tests; Salmonella Infections, Animal; Salmonella typhimurium

The activities of ceftriaxone, moxalactam, and ampicillin against Salmonella typhimurium LT-2 were compared in culture media at pH 5, 6, 7 and 8 and in mice inoculated intraperitoneally. The minimal inhibitory concentrations for strain LT-2 in Mueller-Hinton broth were 0.03 microgram of ceftriaxone per ml, 0.08 microgram of moxalactam per ml, and 0.4 microgram of ampicillin per ml. A comparison of minimal inhibitory concentrations in buffered broth at pH 5 with those in media at higher pH values showed that ceftriaxone was more acid stable than the other antibiotics. Groups of CF-1 female mice inoculated intraperitoneally with 3 X 10(4) colony-forming units received saline or each drug in fourfold decremental doses by the subcutaneous route every 8 h for 3 days, beginning at 24 h after challenge. The mean log 10 colony-forming units of S. typhimurium per spleen at the end of treatment and the mortality rates at 21 days after inoculation were measured for each treatment group. The mean log 10 colony-forming units per spleen was significantly reduced from that of the saline control by dosages of greater than or equal to 0.06 mg of ceftriaxone per kg, 64 mg of moxalactam per kg, or greater than or equal to 16 mg of ampicillin per kg (P less than 0.05). Mortality rates of infected mice were significantly reduced by dosages of greater than or equal to 1 mg of ceftriaxone per kg or greater than or equal to 64 mg of ampicillin per kg (P less than 0.05), whereas moxalactam in dosages as high as 16 mg/kg did not significantly reduce mortality rate. These results demonstrate the superiority of ceftriaxone to the other tested antibiotics on a weight basis in this model of experimental Salmonella infection.

Topics: Ampicillin; Animals; Cefotaxime; Ceftriaxone; Female; Mice; Microbial Sensitivity Tests; Moxalactam; Salmonella Infections, Animal; Salmonella typhimurium; Spleen