Extended-Spectrum β-lactamase-Producing Escherichia coli in Retail Pork and Market Environments: Genetic Diversity and Antimicrobial Resistance in Thailand.

The increasing prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli) highlights the growing issue of multidrug resistance within the food processing chain. This study aimed to determine the prevalence, antimicrobial resistance profiles, molecular genetic structures, and genetic diversity of ESBL-producing E. coli isolated from pork, cutting boards, and knives. A total of 90 samples were collected from 10 local markets in Southern Thailand. ESBL-producing E. coli were identified in 9 samples (10%), with knife samples showing the highest contamination rate (5/90, 5.55%). The ESBL-producing E. coli isolates exhibited high-level resistance to ampicillin (100%), ceftriaxone (88.89%), and cefpodoxime (88.89%), followed by tetracycline (77.78%). Multidrug resistance was detected in 88.89% (8/9) of ESBL-producing E. coli isolates and 28.26% (13/46) of all E. coli isolates. All presumptive ESBL-producing isolates carried ESBL resistance genes (9/9, 100%), with blaCTX-M-1 being the most prevalent (6/9, 66.67%). Additionally, the tetA gene was frequently detected in ESBL-producing E. coli (6/9, 66.67%) and in all E. coli isolates (16/46, 34.78%). Overall, E. coli O157:H7 was identified in 5 isolates (10.87%). The genetic relatedness analysis revealed that five ESBL-producing E. coli isolates were closely related to E. coli ATCC 23502. Our findings confirm a high prevalence of ESBL-producing E. coli carrying resistance genes in knife samples, underscoring the importance of proper sanitary handling practices to minimize microbial contamination in pork retail shops.