Mechanism of Plasmid-mediated Quinolone Resistance in Escherichia coli Isolated from Animal-derived Food
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Abstract:
Escherichia coli was isolated from animal-derived food samples and the antibiotic susceptibility of isolated strains was investigated by agar dilution method. The distribution of plasmid-mediated quinolone resistance (PMQR) genes and mutations in the quinolone resistance-determining region (QRDR) were analyzed by the polymerase chain reaction (PCR) amplification and product sequencing. A total of 179 strains of E. coli were detected (27.7%) in 645 animal-derived food samples. The resistance of these isolates to 15 different antibiotics was observed, with high level of resistance to streptomycin, tetracycline, nalidixic acid, and trimethoprim/sulfamethoxazole. Fourteen strains were PMQR-gene positive, accounting for 7.8% of the test strains, and 11 of the PMQR-positive strains could transfer quinolone resistance to the recipient through conjugation. Mutations in QRDR were prevalent among the PMQR-positive isolates, which could be responsible for the high-level resistance to quinolone. Our results demonstrate that animal-derived food may act as a reservoir for drug-resistant strains and can be a channel for transfer of resistant genes to humans via the food chain, thus causing human infection and a possible outbreak of drug-resistant strains.
