Calcium Peroxide Addition Suppresses ARG Dissemination by Modulating Host Succession and MGE-Mediated Horizontal Transfer During Swine Manure Composting

Applying exogenous additives during composting can help to effectively mitigate the environmental dissemination of antibiotic resistance genes (ARGs). Calcium peroxide (CaO2)-a strong oxidizing agent-has achieved significant efficacy in degrading various pollutants. This study aims to evaluate the effects of CaO2 at varying doses (0, 1% and 3% DW) on the variation in ARGs, mobile genetic elements (MGEs), and bacterial community succession during swine manure composting. Compared to the control (CK), adding 1% and 3% CaO2 reduced total ARGs and MGEs by 50.29% and 64.62% in the LCP and by 68.96% and 79.74% in the HCP treatment, respectively. Adding 1% and 3% CaO2 significantly increased the relative abundances (RAs) of Actinobacteriota and Firmicutes while decreasing those of Proteobacteria and Bacteroidetes during the thermophilic phase, especially under the high-dose treatment. Redundancy analysis (RDA) revealed that MGEs accounted for 54.20% of the total variation in ARGs, followed by environmental factors (30.3%). Network analysis further revealed that 1% and 3% CaO2 treatments disrupted the association between ARGs and their host bacteria. Overall, adding CaO2 can reduce the risks of spreading ARGs in compost products.