Environmental characteristics of antibiotics and antibiotic-resistance genes in the Suzhou River of Shanghai, China

Water quality has continued to improve since the remediation of the Suzhou River in Shanghai, China; however, its new contaminators, such as antibiotics, are less well studied so far. The characteristics and spatial and temporal changes of the contamination status of 13 antibiotics in the water of the Suzhou River were explored. Sampling was carried out at 13 sampling points in two seasons. An analysis was conducted on both the presence and correlation of microbial communities and whether there is a correspondence between antibiotics and changes to antibiotic-resistance genes (ARGs). More than 60% of the antibiotics were detected in both seasons. The total antibiotic concentrations in the river water ranged from 215.2 to 847.7 ng/L. Sulfonamides and fluoroquinolones were detected at a high frequency (100%). In general, the absolute abundance of ARGs was higher from the middle to lower reaches than from the upper to middle reaches of the river. For fluoroquinolone ARGs, qnrS was in the highest level. Also, in sulfonamides ARGs, sul1 and sul2 were commonly detected with the highest frequency (100%). Proteobacteria, Actinobacteriota and Bacteroides were the main bacteria that constituted the correlation network among bacteria, and they existed stably in the winter and the spring. Most antibiotics were significantly correlated with the production of ARGs. Also, antibiotics and ARGs had correlations with microbial community structure. Antibiotics in the Suzhou River were found to pose a high risk to algae, a potential moderate risk to invertebrates and no risk to fish.