Detection of Extended-Spectrum β-Lactamase and Plasmid-Mediated Quinolone Resistance Determinants in Escherichia coli Isolates from Retail Meat in China.

The aim of this study was to investigate the presence of extended-spectrum β-lactamase (ESBL) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli isolated from retail meat samples in Henan Province, China. E. coli isolates were detected in 179 of 645 (27.7%) retail meat samples. Resistance of these isolates to antimicrobials was commonly observed, with 78.2% of isolates resistant to streptomycin, 74.3% resistant to tetracycline and 54.2% resistant to trimethoprim/sulfamethoxazole. Of the 179 isolates, 30 (16.7%) expressed ESBL, with blaTEM-1 (n = 17) and bla(CTX-M-14) (n = 9) most commonly mediating the ESBL phenotype. PMQR genes were present in 14 isolates (7.8%), with qnr and aac(6')-Ib-cr detected alone or in combination in nine (5.0%) and seven isolates (3.9%), respectively. The qnr genes detected included qnrS1 (n = 5), qnrA1 (n = 3), and qnrB4 (n = 1). The qepA gene was absent among these isolates. CTX-M-14 was the most prevalent ESBL type among the PMQR-positive isolates. The qnr and aac(6')-Ib-cr genes were found to co-reside and be co-transferred with blaCTX-M-14 or blaTEM-1 in five isolates. Our data suggest that retail meat may act as a reservoir for multi-resistant E. coli and may facilitate the dissemination of resistance genes.