In-depth characterization of microbiome and resistome of carcasses and processing environments in a swine slaughterhouse.

Antimicrobial resistance represents a critical global health challenge. Within the swine production chain, all stages have been identified as potential reservoirs for antimicrobial resistance genes. In the present study whole metagenomic sequencing technology was applied in a swine slaughterhouse and pig carcasses to investigate microbial communities and their associated antimicrobial resistance genes. Actinomycetota and Pseudomonadota were the dominant phyla across all samples, while Bacillota, Bacteroidota, and Campylobacteriota were more prevalent in the dirty zone and carcass samples than in the clean zone. Key antimicrobial-resistant bacteria included genera such as Acinetobacter, Aeromonas, and Streptococcus, with Acinetobacter spp., Streptococcus suis, and Aliarcobacter cryaerophilus identified as high-priority species for food safety due to their persistence and antimicrobial resistance genes associations. Several genera showed strong correlations with resistance to macrolides, lincosamides, and beta-lactams. Moreover, the plasmid-borne and lateral gene transfer events were associated with dirty zone and carcass samples in comparison to clean zone samples, suggesting the potential dissemination of antimicrobial resistance genes, especially for macrolides and sulphonamides resistance genes. Tetracycline, beta-lactam, and aminoglycoside resistance genes were the most abundant antimicrobial resistance genes across all samples, consistent with a pig slaughterhouse environment. This study highlights distinct microbiome profiles across environmental zones of a pig slaughterhouse, reflecting the adaptation of bacterial taxa to specific processing conditions. The findings have significant implications for food business operators who have to apply appropriate hygienic measures to reduce the dissemination of bacterial food-borne pathogens and to mitigate the risk of antimicrobial resistance transfer along the food chain.