Mycobacterial contamination in tap and shower waters in Thailand

Waterborne disease is increasingly becoming associated with opportunistic premise plumbing pathogens (OPPPs), which can resist residual chlorination, regrow throughout drinking water distribution systems, and colonize premise plumbing. Nontuberculous mycobacteria (NTM) include clinically important species and exert a high burden on healthcare systems. We briefly report a qPCR-based survey of Mycobacterium spp. numbers in tap, POU-treated, and shower waters from Bangkok, Thailand. Non-stagnant tap waters and non-stagnant shower waters had mean numbers of 1.3 × 103 and 2.4 × 103 copies/mL, respectively. Water stagnation resulted in mean numbers higher by up to 1.0 log. The lowest number, 25 copies/mL, was obtained from a POU-treated sample, while the highest number, 2.0 × 104 copies/mL, came from a stagnant tap. Comparing with international data, mean numbers in this study were greater than those in nine out of 11 (82%) comparable studies, and the maximum numbers in this study were also high. Our samples of Bangkok waters exhibited relatively high Mycobacterium spp. numbers, suggesting the need for appropriate POU treatment systems where NTM infection is a health concern. This survey data can be used to set inactivation performance targets in POU water disinfection system design and may also lead to quantitative microbial risk assessment (QMRA) studies.