Fate of antibiotic resistance genes and mobile genetic elements during anaerobic co-digestion of Chinese medicinal herbal residues and swine manure

Swine manure is an important reservoir for antibiotic resistance genes (ARGs) but anaerobic co-digestion (AcoD) can potentially reduce the abundance of these ARGs. However, few studies have considered the effects of Chinese medicinal herbal residues (CMHRs) on the variations in ARGs and mobile genetic elements (MGEs) during AcoD. Thus, this study explored the fate of ARGs and MGEs during the AcoD of CMHRs and swine manure. The results showed that CMHRs effectively reduced the abundances of the main ARGs (excluding ermF, qnrA, and tetW) and four MGEs (by 36.7-96.5%) after AcoD. Redundancy analysis showed that changes in the bacterial community mainly affected the fate of ARGs rather than horizontal gene transfer by MGEs. Network analysis indicated that 17 bacterial genera were possible hosts of ARGs. The results of this study suggest that AcoD with CMHRs could be employed to remove some ARGs and MGEs from swine manure.