Pathogenic bacterial species in tropical Thai swimming pools

ABSTRACT This study investigated the water quality of swimming pools in Thailand, examining the impact of chlorine (Cl), pH, and bather load on pathogenic bacterial growth. Thirty-eight water samples were collected from various swimming pools across Thailand. The water was collected 20 cm below the surface and above the pool floor, at both the pool entrance and the pool rim, between 11:00 and 13:00 h, with pH, number of bathers, and Cl levels were recorded. The water, collected in eight sterilized 250 ml centrifuge bottles with 0.25 mg sodium thiosulfate, was filtered through a 0.22 μm PES sterile disposable filter and transferred to sterile 50 ml conical tubes for DNA extraction and 16S rDNA sequencing, followed by bioinformatic analysis. Linear discriminant analysis effect size identified two bacterial species, such as Gardnerella vaginalis and Sphingomonas koreensis, which were significantly associated with high Cl (p.0.05). The analysis of relative abundance revealed that Blastomonas natatoria was present in 38.6% of commercial pools, while Rickettsia typhi was found in 63% of commercial pools. The study highlights the potential health risks associated with swimming pools, particularly for immunocompromised individuals. Precautions, e.g., maintaining hygiene and avoiding pool water ingestion are recommended to minimize the risk of infection.