Synergistic effects of bio-available heavy metals and antibiotics on the fate of antibiotic resistance genes and the elimination of their compound pollution by chitosan during composting

Purpose Heavy metals (HMs), antibiotics, antibiotic resistance genes (ARGs) and their compound pollutions in manures present a serious threat to ecology and human health. A better solution is urgently sought. In this study, the dynamics change of chitosan addition in chicken manure composting on the profiles of antibiotics and their environmental risk, bio-available heavy metals, ARGs and bacterial communities were investigated. Materials and methods The high-performance liquid chromatography–electrospray ionization tandem mass spectrometry combined with solid-phase extraction, inductively coupled plasma optical emission spectrometry and Wafergen SmartChip Real-time PCR system were used in the scale of 100 kg chicken manure and mushroom bran (1.81:1, fresh weight) composting with chitosan addition. Results and discussion After composting, chitosan addition could completely remove chlortetracycline (CTC) and reduce ofloxacin (OFX) environmental risk to low level (HQ = 0.04) while improving the removal rate of bio-available Cu significantly. Furthermore, it reduced the abundance of pathogens, the amount (18) and absolute abundance (56.7%) of ARGs and the mobile genetic elements (MGEs) compared with traditional compost. Redundancy analysis (RDA) demonstrated that the ranking of environmental factors influencing bacterial community changes is temperature, bio-available Cd, pH, bio-available Cu, OFX and CTC. For the ARGs, bio-available Cu had higher influence than bio-available Cd, and CTC was higher than OFX. Conclusions Our study provides a new strategy on the ARGs, bio-available HMs and antibiotics compound pollution removal with chitosan addition in composting and may guide producing harmless compost production and reutilization of agricultural fishery wastes in the days ahead.