Nontuberculous mycobacteria in drinking water systems - the challenges of characterization and risk mitigation

Abstract

Nontuberculous mycobacteria (NTM) pulmonary infections are a growing concern worldwide, with a disproportionate incidence in persons with pre-existing health conditions. NTM have frequently been found in municipally-treated drinking water and building plumbing, leading to the hypothesis that an important source of NTM exposure is drinking water. The identification and quantification of NTM in environmental samples are complicated by genetic variability among NTM species, making it challenging to determine if clinically relevant NTM are present. Additionally, their unique cellular features and lifestyles make NTM and their nucleic acids difficult to recover. This review highlights a recent work focused on quantification and characterization of NTM and on understanding the influence of source water, treatment plants, distribution systems, and building plumbing on the abundance of NTM in drinking water.

Figure 1.

Dendrogram showing relatedness of NTM species and strains based on rpoB gene sequences. Text colors refer to the types of samples the sequences were obtained from (light blue - home drinking water samples; green – drinking water treatment plant samples; dark blue – sequences found in both home and drinking water samples; orange – water from hospital equipment; yellow – hospital drinking water; red – clinical respiratory samples; black – whole genome sequences at least 85% complete added to NCBI prior to 2015). Sources provided in SI.

Figure 2

Factors influencing NTM concentrations in distribution systems

Figure 3

Overview of possible NTM infection and exposure routes through drinking water and suggested future work needed for NTM infectivity and pulmonary infection prevention.