Evolution and Reduction in Sulfonamide Resistance Genes in Aerobic Compost of Pig Manure

This study identified that the absolute abundance of 15 types of antibiotic resistance genes (ARGs) across 21 organic fertilizer samples ranged between 1.15 × 104 and 6.74 × 1010 copies/g, with sulfonamide ARGs and the intI1 gene exhibiting relatively higher residuals. Subsequent analyses delved into the evolutionary patterns and reduction mechanisms pertinent to sulfonamide ARGs throughout aerobic composting processes. Three bacteria, Bacillus amyloliquefaciens, Bacillus subtilis, and Bacillus velezensis, capable of significantly reducing sulfonamide-resistant bacteria and their sul1 gene were identified. The study revealed that adding composite microbial agent, lowering the pH, or increasing the temperature could inhibit the growth of sulfonamide-resistant bacteria and decrease the abundance of the sul1 gene. Additionally, it was ascertained that the optimization of initial compost pH levels or the incorporation of a compound microbial inoculant effectively reduced the abundance of intracellular and extracellular sulfonamide ARGs and the intI1 gene. The proliferation of Actinobacteria and certain genera during the maturation phase was closely associated with the enrichment of sulfonamide ARGs. This research provides references for the multi-pathway comprehensive control of sulfonamide ARG pollution in composting.