Prevalence and characteristics of extended-spectrum β-lactamase and plasmid-mediated fluoroquinolone resistance genes in Escherichia coli isolated from chickens in Anhui Province, China

Abstract

The aim of this study was to characterize the prevalence of extended-spectrum β-lactamase (ESBL) genes and plasmidmediated fluoroquinolone resistance (PMQR) determinants in 202 Escherichia coli isolates from chickens in Anhui Province, China, and to determine whether ESBL and PMQR genes co-localized in the isolates. Antimicrobial susceptibility for 12 antimicrobials was determined by broth microdilution. Polymerase chain reactions (PCRs), DNA sequencing, and pulsed field gel electrophoresis (PFGE) were employed to characterize the molecular basis for β-lactam and fluoroquinolone resistance. High rates of antimicrobial resistance were observed, 147 out of the 202 (72.8%) isolates were resistant to at least 6 antimicrobial agents and 28 (13.9%) of the isolates were resistant to at least 10 antimicrobials. The prevalence of bla CTX-M, bla TEM-1 and bla TEM-206 genes was 19.8%, 24.3% and 11.9%, respectively. Seventy-five out of the 202 (37.1%) isolates possessed a plasmid-mediated quinolone resistance determinant in the form of qnrS (n = 21); this determinant occurred occasionally in combination with aac(6′)-1b-cr (n = 65). Coexistence of ESBL and/or PMQR genes was identified in 31 of the isolates. Two E. coli isolates carried bla TEM-1, bla CTX-M and qnrS, while two others carried bla CTX-M, qnrS and aac(6′)-1b-cr. In addition, bla TEM-1, qnrS and aac(6′)-1b-cr were co-located in two other E. coli isolates. PFGE analysis showed that these isolates were not clonally related and were genetically diverse. To the best of our knowledge, this study is the first to describe detection of TEM-206-producing E. coli in farmed chickens, and the presence of bla TEM-206, qnrS and aac(6′)-1b-cr in one of the isolates. © 2014 Li et al.