Detection and identification of mycobacteria in the Lisbon water distribution system

Abstract

Mycobacteria have emerged as a major cause of opportunistic infections. Until the present, only a few studies have characterized mycobacteria present in the water distribution system of urban areas. In this study, we characterize these microorganisms in the Lisbon water distribution system. Our results indicate a high rate of positivities (90.5%) with mainly saprophytic mycobacteria. Around 63% of these results belong to strains of Mycobacterium gordonae indicating a generalized proliferation of this species in the Lisbon water distribution system. A total of 21.05% of the isolates are from M. kansasii, M. intracellulare and M. chelonae.

Diversity, Community Composition, and Dynamics of Nonpigmented and Late-Pigmenting Rapidly Growing Mycobacteria in an Urban Tap Water Production and Distribution System

“…M. chelonae has been found in urban water systems worldwide (38,39,59), but its prevalence index and spatial distribution have never been estimated. M. llatzerense has been isolated from tap water samples (59, 62) but has not been detected previously in water distribution networks (34,38,44,59), most probably because this species had not been described at the time when these studies were performed (62). Consistent with our results, M. peregrinum (2,31), M. septicum (31,35,37), and M. salmoniphilum (37,60,63) have been isolated from similar water systems.…”

“…Second, some species were detected at a very low frequency and were detected only because of the large number of isolates analyzed (630 isolates subjected to rpoB sequencing). Previous small-sampling strategies (31,34,35,44) thus gave a biased picture of the RGM community in the water system, underestimating species diversity. Third, recent improvements in molecular identification of RGM allowed us to identify an unprecedented proportion of the isolates by rpoB sequencing and to discover several putative new species (61).…”

“…Mycobacterium chelonae and Mycobacterium fortuitum were the species most frequently detected in previous studies (31,34,35,40,44). However, those previous studies involved only a small number of samples collected from a limited part of the water system considered and provided only qualitative information.…”

“…RGM are commonly recovered from water treatment and distribution systems (31)(32)(33)(34)(35)(36)(37)(38), probably because they can form biofilms (2,(39)(40)(41) and resist chlorination and oligotrophic conditions (42,43). Mycobacterium chelonae and Mycobacterium fortuitum were the species most frequently detected in previous studies (31,34,35,40,44).…”

“…However, those previous studies involved only a small number of samples collected from a limited part of the water system considered and provided only qualitative information. Most of these studies addressed specifically RGM, and few used molecular methods allowing an accurate identification of isolates to the species level (e.g., rpoB or hsp65 gene sequencing) (31,34,40,44). Thus, although there are many reports of RGM detection in water treatment and distribution systems, there are no rigorous and quantitative descriptions of the diversity and spatial distribution of RGM species within these complex systems and no robust information about their clustering into communities.…”