Nontuberculous mycobacteria: an emerging risk in engineered environmental habitats

Nontuberculous mycobacteria (NTM) are microorganisms commonly living in the environment. Nevertheless, most of them are opportunistic pathogens. To verify concentrations of NTM in some man-made habitats, analyses were performed on water and surface samples, and the data were correlated to the global microbiological quality of water. Most of the drinking water samples (98 %) complied with the microbial requirements established by the European Directive 98/83/EC on drinking water when Escherichia coli was considered. Low counts of heterotrophs were also obtained. NTM were isolated from 72 % of the analyzed samples. Tap water from private buildings, schools and hospitals provided positive results for NTM, with comparable densities ranging from 1 to 6 ×10 2 CFU/L. NTM were also found in swimming pool water samples, with concentrations ranging from 29 to 3 ×10 4 CFU/L, as well as in 70 % of the surface sample. The most frequently isolated species were Mycobacterium mucogenicum , M . intracellulare and M . terrae . These yields confirm that no correlation exists between the monitoring controls carried out by law and the occurrence of these bacteria that may represent a potential risk, especially for immunocompromised people and vulnerable groups.