Unraveling the influence of human fecal pollution on antibiotic resistance gene levels in different receiving water bodies using crAssphage indicator gene.

Abstract

Discharged wastewater treatment plant (WWTP) effluents can contaminate receiving water bodies with human feces and alter the abundance of antibiotic resistance genes (ARGs). In this study, we examined the co-occurrence of ARGs, human fecal pollution indicator crAssphage, and antibiotics in human feces and a series of connected receiving water bodies affected by human feces, including water from different treatment units of a WWTP, river, lake, and tap waters. Results showed that crAssphage was detected in 68.2 % of the studied water bodies, confirming widespread human fecal contamination. Both ARG and crAssphage abundances exhibited a distance-decay effect from the emission source to the receiving environment. Interestingly, the detected ARG abundance in the water bodies was significantly correlated with crAssphage abundance but not with the residual antibiotic concentration, demonstrating that the presence of ARG could largely be explained by the extent of fecal pollution, with no clear signs of antibiotic selection. In addition, 14 ARGs co-shared by human feces and water bodies were significantly correlated with crAssphage. Furthermore, a close evolutionary relationship was observed between the blaTEM-1 gene from human feces and aquatic environments. These results imply a potential ARG exchange between human feces and receiving water bodies. Overall, this study provides important insights into the distribution and sources of ARGs in water bodies affected by human fecal contamination.