Lignite as additives accelerates the removal of antibiotic resistance genes during poultry litter composting

Antibiotic resistance genes (ARGs) in animal manure are a great threat to human health. This study investigated the effects of lignite addition at three levels (5%, 10%, 15% w/w) on the profiles of ARGs and the bacterial communities during poultry litter composting. Lignite addition effectively promoted the removal of manure-borne ARGs. After 65 days of composting, the relative abundances of ARGs decreased by 8.9% in control (no lignite), and by 15.8%, 27.7% and 41.5% in 5%, 10% and 15% lignite treatments, respectively. Although the total mobile genetic elements were enriched after composting, the enrichment of the intI-1 gene was significantly lower in the 10% and 15% lignite treatments compared with control. Network analysis indicated that Actinobacteria and Firmicutes were potential bacterial hosts for ARGs. Redundancy analysis showed that bacterial community succession played a key role in the shifts of ARGs. Taken together, this study provides evidence that lignite as additives promoted the removal efficacy of ARGs during composting of poultry litter.