Tracking Extended-spectrum β-lactamase-Producing and Colistin-Resistant <i>Escherichia Coli</i> in Pig Abattoirs: Impacts on Food Safety

The ongoing increase in antimicrobial resistance (AMR) in <i>Escherichia coli</i>, particularly the emergence of extended-spectrum β-lactamase (ESBL)-producing and colistin-resistant strains in livestock, is a significant public health concern. The effectiveness of pig abattoir management, specifically through Hazard Analysis and Critical Control Points (HACCP) protocols, in reducing antimicrobial-resistant contamination continues to be scrutinized. This study investigated the prevalence, characteristics, and critical contamination points of ESBL-producing <i>E. coli</i> (ESBL-Ec) and colistin-resistant ESBL-Ec across the slaughtering processes in two pig abattoirs in Thailand-one operating under HACCP standards and the other certified solely under Good Manufacturing Practices. A higher prevalence of ESBL-Ec was found in the non-HACCP facility (67.98%) compared with the HACCP facility (52.04%), especially in pig carcasses. Skin and carcass washing in HACCP facilities effectively decreased bacterial contamination. Conversely, non-HACCP facilities should implement measures such as cleaning skin with disinfectants at the lairage, regularly monitoring and adjusting the final washing protocol, and strict sterilization of chopping plates to effectively control contamination points. Most ESBL-Ec isolates were multidrug-resistant and carried <i>bla</i> _CTX-M group 1 or group 9 genes. Additionally, 12.6% of these isolates were resistant to colistin, with the <i>mcr-1</i> gene predominantly identified. ST10 was the dominant clone of <i>mcr</i>-carrying ESBL-Ec across various slaughtering stages and sample types. These findings highlight the importance of implementing HACCP protocols to reduce contamination, enhance food safety, and mitigate public health risks. Ongoing AMR monitoring to find critical points along the slaughtering process is essential to reduce sources of AMR transmission to consumers.