Plasmid-mediated quinolone resistance and β-lactamases in Escherichia coli from healthy animals from Nigeria

Abstract

Objectives: The animal reservoir of plasmid-mediated quinolone resistance (PMQR) and β-lactamases is still controversial and little information is available on the prevalence of these resistance determinants in developing countries. The aim of this study was to identify and characterize PMQR and β-lactamases in a collection of commensal ampicillin-resistant Escherichia coli isolated from healthy chickens and pigs at slaughter, collected in November-December 2006, in Ibadan, Nigeria.

Methods: One hundred and sixty-two ampicillin-resistant E. coli were obtained from healthy chickens and pigs at slaughter in Ibadan, Nigeria. Strains were tested for antimicrobial susceptibility by disc diffusion assay. MICs of ciprofloxacin were determined by Etest. Resistance genes were screened by PCR and DNA sequencing. Clonal relatedness of the isolates was determined by enterobacterial repetitive intergenic consensus-PCR. Plasmids were transferred by conjugation and transformation and characterized by PCR-based replicon typing and plasmid multilocus sequence typing.

Results: PMQR genes were detected in 18 E. coli strains; 11 of them showed reduced susceptibility to ciprofloxacin. Twelve strains carried qnrS1, three strains carried qnrB19, one strain carried qnrB10 and three strains carried qepA; one strain carried both qepA and qnrB10. All strains carried the bla(TEM) gene; one strain was positive for the CTX-M-15 extended-spectrum β-lactamase.

Conclusions: Our findings suggest that food animals could represent an important reservoir of PMQR in this region of Africa. Previous studies reported high prevalence of qnr genes in clinical isolates from humans in Nigeria, suggesting that the spread of these resistance determinants in this country could be particularly relevant.