Occurrence and diversity of nontuberculous mycobacteria affected by water stagnation in building plumbing

Abstract

Nontuberculous mycobacteria (NTM) refer to mycobacteria other than Mycobacterium tuberculosis and Mycobacterium leprae. Some NTM are known to cause pulmonary and skin diseases. As NTM are prevalent in water supply systems, the health burden of waterborne NTM is concerned. However, little is known about the occurrence and diversity of NTM in building plumbing, especially after water stagnation. This study revealed the abundance and diversity of NTM in building plumbing by using culture-dependent and culture-independent approaches. Moreover, the chlorine susceptibility of NTM isolates in tap water was evaluated. The increase in the abundance of Mycobacterium spp. was observed in some taps after 24 h of stagnation, indicating that NTM could have the potential to regrow in building plumbing. While Mycobacterium mucogenicum and Mycobacterium avium were detected by cultivation, amplicon sequencing of NTM-specific hsp65 genes revealed that Mycobacterium gordonae was dominant in most of the samples, which was not detected by cultivation. The chlorine susceptibility experiment demonstrated that NTM strains related to M. avium and M. mucogenicum were 119 and 426 times more tolerant to chlorine than Escherichia coli, respectively. As M. mucogenicum, M. avium, and M. gordonae are regarded as opportunistic pathogens, intensive monitoring of NTM in tap water in building plumbing is necessary.