Insights into antibiotic resistomes from gut metagenome-assembled genomes of the free-range pigs

ABSTRACT The pig gut microbiome serves as a reservoir for antibiotic resistance genes (ARGs), which pose a threat to public health and environmental safety. To investigate the presence of ARGs carried by free-range pigs, which have frequent contact with humans and their environment, we characterized the resistome of the pig gut microbiome through metagenomic sequencing of fecal samples from 120 pigs across four provinces in China (Yunnan, Guizhou, Sichuan, and Jiangsu). By constructing metagenome-assembled genomes (MAGs) and gene catalogs, we explored the microbial community structure and ARG distribution. Our analysis revealed a highly diverse array of ARGs, particularly those conferring resistance to multidrug, glycopeptide, peptide, and tetracycline antibiotics. Bacillota A and Actinomycetota were the dominant phyla across samples. However, notable regional differences in microbiota composition and resistance profiles were observed. These differences were likely influenced by local farming practices and environmental conditions. Guizhou harbored 11 unique ARG types, followed by Sichuan (seven), which showed region-specific resistome signatures. Escherichia coli and other microbial taxa were closely linked with ARG abundance, suggesting potential vectors for horizontal gene transfer. Analysis of mobile genetic elements (MGEs) further supported this, revealing a strong linear correlation between MGE and ARG abundance, with transposase elements particularly associated with multidrug ARGs. These findings highlight the central role of MGEs in ARG dissemination and underscore the need for targeted strategies to curb antibiotic resistance in livestock systems. Regional variation in resistome profiles further emphasizes the influence of local agricultural practices on resistance dynamics. IMPORTANCE The growing prevalence of antibiotic resistance poses a significant global health threat, making it imperative to trace the origins and transmission routes of ARGs. This study delivers a comprehensive genomic reference for the porcine gut microbiota and clarifies how regional farming practices shape distinct resistome profiles. Integrating these data with analyses of mobile genetic elements and microbial hosts reveals the complex interplay among host, microbiota, and environment, thereby extending current knowledge of the pig gut ecosystem. These findings provide an evidence-based foundation for targeted surveillance and intervention strategies to curb antibiotic resistance in livestock and safeguard public health.