Identification of nontuberculous mycobacteria in home drinking water network in the Metropolitan Region of Chile

Abstract

Background: Nontuberculous mycobacteria (NTM) are widely distributed in the environment and some species are opportunistic pathogens. The incidence of NTM disease has shown an upward trend, particularly among immunocompromised patients. Aim: To identify the presence of NTM in the drinking water system in Chile’s Metropolitan Region (MR). Methods: 110 home drinking water samples from 33 communes were collected and analyzed for NTM. After a filtration and decontamination protocol, the samples were cultured in Middlebrook 7H11 medium. Species were identified by MALDI-TOF and 16S RNA sequencing. Results: 30.9% (34/110) of the water samples tested positive for NTM, resulting in the identification of 45 isolates. Mycobacterium from the mucogenicum group constituted the majority with 51.1% (23/45), followed by Mycobacterium frederiksbergense with 15.6% (7/45) and M. fluoranthenivorans with 11.1% (5/45). NTM with pathogenic potential were also identified, such as M. chelonae (n=3), M. fortuitum (n=1), and M. kansasii (n=1).  Conclusions: This study shows that NTM isolation is prevalent in drinking water in the MR. Some species encountered are rarely pathogenic; however, it is important to consider the presence of NTM with opportunistic potential in immunocompromised hosts.

Keywords: non-tuberculous mycobacteria; drinking water; environmental mycobacteria; MALDI-TOF MS