Occurrence of antibiotics in the main rivers of Shenzhen, China: Association with antibiotic resistance genes and microbial community.

The occurrence and distribution of antibiotics were investigated in surface water and sediment collected from the main rivers of Shenzhen, China. Total concentrations of 20 selected antibiotics ranged from 36.510 to 1075.687 ng L-1 (mean 244.992 ng L-1) in 31 water samples and from 28.124 to 2728.810 ng g-1 (mean 680.169 ng g-1) in 31 sediment samples. Notably, STZ and SDZ were the dominant antibiotics in both water and sediment as their higher concentrations compared with the other compounds. Furthermore, comprehensive profiling of antibiotic resistance genes (ARGs) and microbial community was performed to gain an understanding of the evolution and dissemination of ARGs in microbial communities caused by the occurrence of antibiotics in sediment samples from Maozhou River. As a result, the sul1 gene was found to be the most abundant ARG and Proteobacteria was the most abundant microorganism in all the samples (37.4-51.7%), followed by Bacteroidetes (15.3-18.4%). Statistical analysis figured out the relations among antibiotics, ARGs and microbial community. A specific conclusion could be drawn from the positive correlations among the bla_d gene, Fusobacteria, and sulfamethoxazole. It suggests that antibiotics may be positively linked to the expression of ARGs in certain bacteria, and thus high reproduction would occur within the bacterial community. Overall, the widespread distribution of ARGs underscores the need for further research on the mechanism of antibiotics influence as emerging contaminants in the environment and the associated risks to microbial community.