Mitigating the risk of antibiotic resistance and pathogenic bacteria in swine waste: the role of ectopic fermentation beds

Abstract

The ectopic fermentation bed (EFB) is used to recycle animal waste, but the fate and dynamic change of antibiotic resistance genes (ARGs) with biocide or heavy metal resistance genes (B/MRGs) and pathogens remain unclear. We performed metagenomic sequencing on 129 samples to study the resistome and bacteriome in pig feces from 24 farms, comparing these profiles with EFBs from five farms, and one farm's EFB was monitored for 154 days. Results showed pig feces from different cities (Chengdu, Meishan, and Chongqing) shared 284 of 311 ARG subtypes, with over 70% being high-risk ARGs, and 106 of 114 pathogenic bacteria. Swine farms were heavily contaminated with co-occurrences of risky ARGs, B/MRGs, and pathogenic hosts, particularly Escherichia coli and Streptococcus suis being hosts of multidrug ARGs. The application of EFBs markedly mitigated these risks in feces, showing a 3.09-fold decrease in high-risk ARGs, a 72.22% reduction in B/MRGs, a 3.95-fold drop in prioritized pathogens, an 89.09% decline in the relative abundance of pig pathogens, and a simplification of their correlation networks and co-occurrence patterns. A mantel analysis revealed that metal contents (Fe, Mn, and Cu) and time influenced pathogen and ARG profiles. Pathogens, ARGs, and risk ARGs exhibited periodic variations, peaking at days 14, 84, and 154, with 70-day intervals. This study provides a comprehensive assessment of the risks associated with pig feces and EFBs and demonstrates that EFBs reduce ARG risks by inhibiting their associations with B/MRGs and pathogens. These findings can help guide and improve the management of antimicrobial resistance and pathogenic contaminants in EFB applications to reduce environmental pollution.