The present study aimed to characterize the extended-spectrum β-lactamases and plasmid-mediated AmpC β-lactamases (ESBL/PMAβ) among Escherichia coli producers isolated from beef, pork, and poultry meat collected at retail, in Portugal. A total of 638 meat samples were collected and inoculated on selective medium for the search of E. coli resistant to 3rd generation cephalosporins. Isolates were characterized by antimicrobial susceptibility testing, molecular assays targeting ESBL/AmpC, plasmid-mediated quinolone resistance (PMQR), and plasmid-mediated colistin resistance (PMCR) encoding genes. The highest frequency of E. coli non-wild type to 3rd generation cephalosporins and fluoroquinolones was observed in broiler meat (30.3% and 93.3%, respectively). Overall, a diversity of acquired resistance mechanisms, were detected: blaESBL [blaCTX-M-1 (n = 19), blaCTX-M-15 (n = 4), blaCTX-M-32 (n = 12), blaCTX-M-55 (n = 8), blaCTX-M-65 (n = 4), blaCTX-M-27 (n = 2), blaCTX-M-9 (n = 1), blaCTX-M-14 (n = 11), blaSHV-12 (n = 27), blaTEM-52 (n = 1)], blaPMAβ [blaCMY-2 (n = 8)], PMQR [qnrB (n = 27), qnrS (n = 21) and aac(6')-Ib-type (n = 4)] and PMCR [mcr-1 (n = 8)]. Our study highlights that consumers may be exposed through the food chain to multidrug-resistant E. coli carrying diverse plasmid-mediated antimicrobial resistance genes, posing a great hazard to food safety and a public health risk.
Keywords: ESBL/AmpC; Escherichia coli; PMQR; antimicrobial resistance; mcr genes; meat.