Characterisation of plasmids harbouring qnrA1, qnrS1, and qnrB4 in E. coli isolated in the Philippines from food-producing animals and their products.

OBJECTIVES

Determinants showing plasmid-mediated quinolone resistance, which usually leads to antimicrobial ineffectiveness, have become an emerging clinical problem. In our previous study in the Philippines, a high prevalence of qnr determinants was found in clinical samples and food-producing animals and their food products. However, no qnr-carrying plasmids have been investigated in animals or animal-derived foods. Hence, in the present, we aimed to characterise qnr-carrying plasmids in Escherichia coli isolated from the food supply chain.

METHODS

Plasmids from 44 qnr-positive isolates were assigned to incompatibility groups by Polymerase chain reaction (PCR)-based replicon typing, and the presence of β-lactamase-encoding genes were investigated by PCR. Localisation of qnr in plasmids was determined by S1-PFGE and Southern blot hybridisation. The transferability of qnr-carrying plasmids was examined by conjugation analysis.

RESULTS

Overall, 77.3% (95% confidence interval [CI]: 62.2-88.5) of the isolates harbouring qnr determinants were positive for seven plasmid types, and 56.8% concurrently harboured blaTEM-1. Plasmid IncFrepB was prevalent (65.9% [95% CI: 50.1-79.5]) among qnr determinants. Localisation of qnr determinants in IncFrepB and transferability of plasmids was further confirmed.

CONCLUSION

The current study proved that qnr in E. coli isolated from food-producing animals and their food products could spread via plasmid IncFrepB upon selective pressure with quinolones or other antimicrobials. Therefore, to curb the emergence and spread of qnr-harbouring bacteria in the Philippines, prudent use of antimicrobials in animal production and stricter hygiene and food handling are recommended.