Research progress of antibiotic resistance genes in wastewater treatment plants

Antibiotic resistance genes (ARGs) are emerging contaminants which pose a great threat to the environment and human health. As an important source and sink of ARGs, wastewater treatment plants (WWTPs) have great potential ecological risks. Therefore, the diversity, composition as well as transfer mechanism of ARGs in the wastewater treatment processes were systematically introduced. ARGs of beta-lactam, macrolide, tetracycline, sulfonamide and aminoglycoside were widely detected in global WWTPs. However, the abundance of different types of ARGs along treatment processes and dominant ARGs detected in each process were different. Horizontal transfer was the main transfer mechanism of ARGs. The effects of common factors such as environmental conditions, influent wastewater quality and operational parameters on the abundance and distribution of ARGs were also summarized. It was proposed that the focus of future research was identifying the representative ARGs and the most influencing factors, quantifying the effects of various factors on the abundance, compositions and horizontal transfer mechanisms of ARGs, and establishing a standard system for evaluating the risks of ARGs for monitoring and controlling the potential ecological risks of ARGs in WWTPs.