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

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.