Ozone cooling phase treatment inhibit the rebounding of ARGs by hosts elimination during swine manure composting

Antibiotic resistance genes (ARGs) residual in composting products pose a global threat to public health. The ARGs rebounding during cooling and mature phase of composting has been recognized as a critical barrier to controlling antibiotic resistance in composting systems. However, strategies to specifically inhibit the ARGs rebounding in the later stage of composting remain poorly understood. In this study, we optimized ozone treatment during the cooling phase of swine composting and identified 0.6 g/kg fresh weight (FW) as the optimal dosage. The absolute and relative abundance of ARGs were reduced by 50.34 % and 60.33 %, respectively, compared with control (p < 0.001). The suppression of ARGs hosts, including Pseudomonas, Lactobacillus, Clostridium, and Actinomycetales_unclassified, contributed substantially to ARGs reduction, particularly for intercellular ARGs (sul1、sul2、sul3、gyrA、ermF). Concurrently, microbial horizontal gene transfer (HGT) potential was mitigated through targeted inhibition of microorganisms harboring Type IV secretion system (particularly Pseudomonas). Furthermore, the demonstrated economic viability, operational safety, and ease of system retrofitting and technological upgrading support the theoretical feasibility of implementing ozonation in aerobic composting as an effective strategy for ARG mitigation.