[Prevalence and characterization of cefotaxime and ciprofloxacin co-resistant Escherichia coli isolates in retail chicken carcasses].

OBJECTIVE:To investigate the prevalence and characteristics of cefotaxime in co-resistant Escherichia coli isolates in retail chicken samples and provide or the risk assessment and evaluation of new control measures of multi-drug i isolates in retail chicken products. METHODS:Whole chicken carcasses re collected from Shanxi (n = 91), Guangdong (n = 63) and Inner 53) from April to December in 2011, cefotaxime and ciprofloxacin co- li isolates were recovered and subjected to phylogenetic group typing and usceptibility testing. All isolates were further characterized by screening for genes, quinolone resistance determinants by PCR and followed by DNA sis. RESULTS:Cefotaxime and ciprofloxacin co-resistant E. coli isolates in 35.7% (73/207) of retail chicken carcasses. E. coli isolates of oup A were dominant (61.6%, 45/73) and all the isolates showed tant profiles. The dominant resistant profiles were AMP-CAZ-CTX-CIP- (n =34) and AMP-CAZ-CTX-CIP-CHL-GEN-SXT-TET (n = 24). Point and ciprofloxac mutations in quinolone resistance determination, regions of topoisomerases were identified in all the isolates and most of the isolates accumulated three (n = 56) or four (n = 12) point mutations. Plasmid mediated quinolone resistant determinants were identified in 50 isolates, including oqxAB (n = 48) , aac(6')-Ib-cr (n = 5) , qnrS1 (n = 5) and qnrS2 (n = 3). Six subtypes of blaCTX-M were identified in 72 E. coli isolates and blaCTX-M-55 (n = 62) was dominant. CONCLUSION:Retail chicken could serve as an important reservoir of cefotaxime and ciprofloxacin co-resistant E. coli isolates.