Effects of Reclaimed Water Supplementation on the Occurrence and Distribution Characteristics of Antibiotic Resistance Genes in a Recipient River

Due to the serious scarcity of water resources and the aggravation of water pollution in northern China, replenishing reclaimed water can alleviate the water shortage problem in northern rivers to a certain extent, but has also become an important way for antibiotic resistance genes (ARGs) to spread into rivers. In order to study the characteristics of ARGs in reclaimed water recharge rivers (Wenyu River), the abundance and distribution of ARGs in a typical reclaimed water replenishment river were analyzed by metagenomic sequencing technology combined with river water quality. The results showed that: due to the input of reclaimed water, the water quality characteristics of downstream sampling points of the river were significantly different from those upstream. Water quality factors such as total organic carbon, chemical oxygen demand, chlorophyll, and total nitrogen tended to increase gradually. Quinolones and macrolides were the main types of antibiotics. A total of 1217 ARGs were detected in the reclaimed water river system, including multidrug resistance, macrolide-lincosamide-streptogramin (MLS), tetracycline, glycopeptide, peptide, aminocoumarin, etc. The average abundance of ARGs in reclaimed water was higher than that in rivers. Among them, multidrug ARGs existed most widely, which may gradually become the main trend of ARGs' evolutionary variation. RDA results revealed that the environmental factors EC and DO, as well as tetracycline antibiotics (TCs), may be important environmental factors affecting the distribution of ARGs.