Antimicrobial resistance reservoirs in salmon and broiler processing environments, sidestreams, and waste discharges

This study mapped antimicrobial resistance (AMR) reservoirs in salmon and broiler processing plants by analyzing sidestream materials, waste discharges, and processing environments. Using targeted sequencing, researchers identified a wide variety of AMR genes, including high-risk ones such as TolC, mdtE, tet(L), tet(M), mecA, and blaCTX-M-1. The greatest diversity (32–330 unique genes) was found in wastewater and sludge. Over 300 bacterial isolates were recovered, mainly Enterobacterales, Enterococcus, and Pseudomonas spp. While most showed low resistance, quinolone-resistant and multidrug-resistant E. coli were detected in broiler plant effluents, with whole genome sequencing confirming plasmid-borne resistance genes. The findings indicate that food industry wastewater is a significant pathway for releasing AMR genes and bacteria into the environment, posing risks of re-introduction into production systems despite relatively low prevalence among isolated bacteria.