Prevalence of antibiotic resistance genes in drinking water and biofilms: The correlation with the microbial community and opportunistic pathogens.

The emergence of antibiotic resistance genes (ARGs) and opportunistic pathogens (OPs) in drinking water system posed potential risks to human health. However, the occurrence of ARGs and OPs in drinking water biofilms is still at its infancy. In this study, we investigated the occurrence of ARGs and OPs in both water and biofilm samples from a drinking water system, and the correlation between ARGs and microbial communities was analyzed. The quantitative PCR results showed that the drinking water treatment process effectively decreased the absolute abundances of ARGs. However, the relative concentration of ARGs did not show a significant difference between raw water and treated water samples. Compared with bulk water and tap water samples, biofilms had higher relative abundances of ARGs. 16 S Illumina Miseq sequencing results showed that microbial communities of biofilms were distinguished with water samples. Meanwhile, qPCR results of OPs also showed that biofilms had higher relative abundances of OPs compared with water samples. Furthermore, the Spearman correlation analysis indicated that Dechloromonas, Desulfovibrio, Methylobacterium and Propionivibrio correlated well with the relative abundance of ARGs. The absolute concentrations of OPs and ARGs also showed a significant correlation. Results of this study suggest that biofilms could serve as the reservoirs for the spread of ARGs and the interaction between biofilms and bulk water requires further research.