Mycobacteria acquisition from potablewater across the drinking water system in Australia

Abstract

Background: Nontuberculous mycobacteria (NTM) can be readily isolated from water samples, however there is limited data regarding the extent of NTM isolation throughout drinking water distribution systems (DWDS) from treatment plant to point of use (POU). This study has two aims, 1) to define the extent of NTM colonization, with a focus on Mycobacterium abscessus group (Mabs), in two DWDS, and POU outlets in four major hospitals and homes of persons with Mabs infections, and 2) to determine if Mabs strains present in persons with Mabs infection are the same as those in their potable water. Methods: Water samples were collected from four hospitals (including 2 with large CF centres and 2 with additional chlorination treatment), drinking water distribution systems (including a sub-tropical and temperate location) and the homes of participants with Mabs pulmonary disease (n = 53) including people with CF (n = 11) between 2021 and 2023. Sampling of homes was undertaken on a single occasion, whereas, for hospital and DWDS on multiple occasions over two years. NTM was concentrated via filtration and cultured onto a range of media, treated with antimicrobials to reduce the overgrowth of non-NTM organisms and growth supplements to enhance the growth and recovery of NTM [1]. Genome comparisons of Mabs isolated from the household water samples with the participant's clinical isolate(s) was performed. Results: Overall, 67.0% of the water samples cultured NTM species and 31.2% were positive for ≥2 species. A total of 33% of water samples only cultured environmental (ENV) NTM and 22.4% cultured ENV and clinically relevant (CLIN) NTM. CLIN NTM were isolated from 11.6% samples, and 14.5% of all samples were Mabs-positive) (Table). Mabs was isolated from 48% of all participant homes. Of these, 44.4% isolated Mabs from >1 site, most commonly showers, water filters and outdoor taps. Rates of Mabs (and CLIN NTM) were lower in 2 hospitals (with additional treatment) compared to the other 2 hospitals. Similarly, Mabs (and CLIN NTM) were less common in the temperate DWDS than the sub-tropical DWDS. Whole genome sequence data confirms globally distributed Mabs strains are commonly detected in the drinking water (in home, hospitals and DWDS). Conclusions: NTM species can be readily isolated from multiple levels of thewater distribution system. Mabswas commonly isolated from homes of people with Mabs disease. Two hospitals, those with on-site chlorination, had very low rates of Mabs colonization and lower species diversity. Fewer NTM were recovered from the DWDS in a temperate climate compared to the DWDS in the sub-tropical climate. Acknowledgements: Funding: Cystic Fibrosis Foundation, USA (BELL19A), NHMRC (1102494).