High carriage of plasmid-mediated quinolone resistance (PMQR) genes by ESBL-producing and fluoroquinolone-resistant Escherichia coli recovered from animal waste dumps

Abstract

Abstract There have been a rapid rise in the consumption of quinolones in human and veterinary medicine recently. This has contributed in no small measure to the rising incidence of quinolone resistance in bacteria. This study investigated the antibiotic resistance and carriage of plasmid-mediated quinolone resistance (PMQR) determinants by ESBL-producing E. coli obtained from the animal waste dumps of an agricultural farm. Isolation of ESBL-producing E. coli from the animal waste samples was done on CHROMagar ESBL, while presumptive isolates were picked and identified using molecular method (detection of uidA gene). Susceptibility to a panel of ten antibiotics was done using disc diffusion method, and detection of PMQR genes (qnrA, qnrB, qnrS, aac(6')-lb-cr, qepA and oqxAB) was done using primer-specific PCR. A total of twenty-five ESBL-producing E. coli was obtained from the cattle (6), piggery (7) and poultry (12) waste dumps of the farm. There was 100% resistance by the isolates to cefpodoxime, cefotaxime, enrofloxacin, trimethoprim-sulfamethoxazole and penicillin, while no resistance was observed to amoxicillin-clavulanate and imipenem. The resistance by the isolates to ceftazidime and streptomycin was 24% and 48% respectively. The frequency of detection of PMQR genes in the isolates was: qnrA (96%), qnrB (88%), qnrS (88%), aac(6')-lb-cr (80%), qepA (80%) and oqxAB (96%). This findings showed a high level of antibiotic resistance and PMQR genes in the ESBL-producing E. coli in this study; suggesting that animal waste dumps in agricultural farms could be a budding ‘hotspot’ for antibiotic resistant bacteria and resistance genes.