Effects of Chinese herbal medicine residues on antibiotic resistance genes and the bacterial community in chicken manure composting

Abstract

Livestock manure is an important way that antibiotic resistance genes (ARGs) can enter the environment, and composting is an effective method for removing ARGs from livestock manure. In this study, different volume ratios of Chinese medicinal herbal residues (CMHRs) were added to laboratory-scale chicken manure composting to evaluate their effects on the behavior of ARGs, mobile genetic elements (MGEs), and the bacterial community. At the end of the composting period, the structure of the microbial community changed. Firmicutes decreased and Bacteroidetes increased. The relative abundance of the 21 ARGs and 5 MGEs detected decreased by varying degrees in the different treatments (except for sulI and intI1). The removal rate of the ARGs increased with the increased addition of CMHRs. The correlations between transferase genes (tnpA and tnpA-02) and ARGs were significant (p < 0.05); therefore, transposon plays an important role in the horizontal gene transfer of ARGs in chicken manure. The results imply that CMHRs would be an effective bulking agent for the removal of ARGs from chicken manure composting.