Detection of mutations in the gyrA and parC genes in Escherichia coli isolates carrying plasmid-mediated quinolone resistance genes from diseased food-producing animals

DNA Topoisomerase IV Swine Diseases 0301 basic medicine China Swine Escherichia coli Proteins R Factors Gene Expression Regulation, Bacterial Quinolones Anti-Bacterial Agents 3. Good health 03 medical and health sciences Ducks DNA Gyrase Drug Resistance, Multiple, Bacterial Mutation Escherichia coli Food Microbiology Animals Chickens Escherichia coli Infections Poultry Diseases
DOI: 10.1099/jmm.0.043307-0 Publication Date: 2012-08-10T04:49:41Z
ABSTRACT
In this study, the prevalence of plasmid-mediated quinolone resistance (PMQR) was investigated in 495 Escherichia coli isolates from diseased food-producing animals in Guangdong province, China. The quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes were analysed for mutations in 55 isolates harbouring only oqxAB and all isolates harbouring other PMQR genes. Overall, 282 (57.0 %) E. coli isolates had at least one PMQR gene. oqxAB was detected in 215 isolates and predominated the PMQR genes, followed by qnrS (63 isolates), aac(6')-Ib-cr (56 isolates), qnrB (39 isolates) and qepA (18 isolates). qnrA, qnrC and qnrD were not found in any of the isolates. The rates of resistance to ciprofloxacin, enrofloxacin, levofloxacin and nalidixic acid were 75.2, 81.0, 70.5 and 97.4 %, respectively, among the 495 isolates. Eight types of mutation in gyrA were detected in 154 PMQR-positive isolates, and 147 isolates were found to have mutations in parC. PFGE analysis indicated that the PMQR-positive E. coli isolates were genetically diverse. This study demonstrated that the number of mutations in QRDRs of gyrA and/or parC was significantly associated with the MICs of quinolones (P<0.01). The rates of resistance to ciprofloxacin, enrofloxacin and nalidixic acid in PMQR-positive isolates were significantly higher than those in PMQR-negative isolates (P<0.05). In addition, the prevalence of oqxAB had significant Spearman correlation coefficients in relation to the MICs of all four tested quinolones (P<0.01).
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