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 beta-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. (C) 2022 The Authors. Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy.