Dissemination of antibiotic resistance genes in swimming pools and implication for human skin.

Swimming pools are crowd-gathering places that are associated with numerous outbreaks of water-borne diseases. Herein, we investigated the distribution of antibiotic resistance genes (ARGs) and bacterial communities in swimming pools and determined the influencing factors and potential human exposure. Sixteen swimming pools with different bather loads (0.01-0.16 person/m2·h) were investigated. Water samples were collected, before opening and after closing of the facilities, from six swimming pools, and skin samples were collected from volunteers. Comprehensive approaches, high-throughput qPCR and 16S rRNA gene sequencing, were used. The results showed that swimming pools contained a higher relative abundance (0.62 gene copies/16S rRNA) and absolute abundance (6.57×108 gene copies/L) of ARGs on average. Bather loads contributed to the increase of core ARGs, and the absolute abundance of ARGs significantly increased by 1.47-1.94 orders of magnitude when the bather load was more than 0.1 person/m2·h. Dermal contact was estimated as the main exposure route of ARGs. Eighteen ARGs that were not detected before swimming were found on human skin and remained after showering. Furthermore, the event intake burden of ARGs via dermal contact was higher than that via ingestion when swimming. This study provides an assessment of ARGs and antibiotic-resistant bacteria (ARB) in swimming pools and helps to define the health risks to swimmers.