Occurrence and contamination profiles of antibiotic resistance genes from swine manure to receiving environments in Guangdong Province southern China.

Livestock farms are commonly regarded as the main sources of antibiotic resistance genes (ARGs), emerging pollutants with potential implications for human health, in the environment. This study investigated the occurrence and contamination profiles of nine ARGs of three types from swine manure to receiving environments (soil and water) in Guangdong Province, southern China. All ARGs occurred in 100% of swine manure samples. Moreover, the absolute concentration of total ARGs varied from 3.01 × 10 to 7.18 × 10 copies/g, which was significantly higher than that in wastewater and manured soil (p < 0.05). Regarding the distribution characteristics of ARGs in swine manure, wastewater and manured soil, the tetracycline resistance gene tetO was predominant. ARGs in swine manure were relatively stable among swine growth periods after the nursery period. The ARG concentration did not differ significantly between manured and unmanured soil (p > 0.05). However, the number of ARGs (ermB, qnrS, acc(6')-Ib, tetM, tetO and tetQ) decreased but were not eliminated by wastewater treatment components (p < 0.05). Based on correlation analysis, the tetracycline resistance genes tetQ and tetW in swine manure and the macrolide resistance genes ermB and ermF in wastewater were more easily spread than were other ARGs onto soil when the substances were applied as fertilizers. Therefore, effective removal and a standard permissible environmental level of ARGs should be established to control the risk of spreading ARGs in the environment.