Exploring the antibiotic resistance genes removal dynamics in chicken manure by composting

Prolonged antibiotic usage in livestock farming leads to the accumulation of antibiotic resistance genes in animal manure. Composting has been shown as an effective way of removing antibiotic resistance from manures, but the specific mechanisms remain unclear. This study used time-series sampling and metagenomics to analyse the resistome types and their bacterial hosts in chicken manures. Composting significantly altered the physicochemical properties and microbiome composition, reduced antibiotic resistance genes by 65.71 %, mobile genetic elements by 68.15 % and horizontal gene transfer frequency. Source tracking revealed that Firmicutes, Actinobacteria, and Proteobacteria are the major bacterial hosts involved in the resistome and gene transfer events. Composting reduces the resistome risk by targeting pathogens such as Staphylococcus aureus. Structural equation modelling confirmed that composting reduces resistome risk by changing pH and pathogen abundance. This study demonstrates that composting is an effective strategy for mitigating resistome risk in chicken manure, thereby supporting the One Health initiative.