Effect of hydraulic conditions on the prevalence of antibiotic resistance in water supply systems.

The incidence of antibiotic resistance genes (ARGs) in tap water leads to potential risks to human health and draws more and more attention from the public. However, ARGs harbored in drinking water remain largely unexplored. In this study, a simulated water supply system was designed to study the effects of different pipe flow rates on the transmission of antibiotic resistance in water supply systems. We observed that the biofilm in low flow rate pipeline (0.1 m/s, 0.3 m/s) had higher concentration of both antibiotic resistant bacteria (ARB) and ARGs, while high flow rate (0.5 m/s and 0.7 m/s) resulted in low relative abundance of ARB and high relative abundance of ARGs in biofilms. The results showed that the high flow rate led to an abundance in non-culturable bacteria and a scarcity of nutrients in the biofilm, giving rise to its antibiotic resistance. High-throughput sequencing pointed out that the high content of Caulobacteraceae and Paenibacillus were determined in biofilms of high flow rate pipelines. Similarity analysis of microbial community composition of inlet water (IW), biofilms and outlet water (OW) showed that the composition of microbial community in OW was more similar to that in biofilms than in IW. Genera of bacteria in biofilms and OW (Brevundimonas, Brevibacillus and Pseudomonas) which had relationship with sulⅠ, sulⅡ in biofilms (P < 0.05) had higher relative abundance than that in IW. Different flow rate conditions had an impact on the biomass, microbial community, ARB and ARGs composition of biofilms. Thus, the detachment of biofilms can increased the antibiotic resistance of the water.