Occurrence of potentially pathogenic nontuberculous mycobacteria in Mexican household potable water: a pilot study

Abstract

Background: Nontuberculous mycobacteria (NTM) are environmental opportunistic pathogens found in natural and human-engineered waters, including drinking water distribution systems and household plumbing. This pilot study examined the frequency of occurrence of NTM in household potable water samples in Mexico City. Potable water samples were collected from the "main house faucet" and kitchen faucet. The presence of aerobic-mesophilic bacteria (AMB), total coliforms (TC), fecal coliforms (FC) and NTM species were determined. Mycobacteria species were identified by PCR restriction enzyme pattern analysis (PRA) of the 65-kDa heat shock protein gene (hsp65) and sequencing of the hypervariable region 2 (V2) of the 16S rRNA gene and of the rpoB gene.

Results: AMB (<100 CFU/ml) were present in 118 out of 120 samples; only two samples were outside guidelines ranges (>100 CFU/ml). TC and FC were detected in four and one samples, respectively. NTM species were recovered from 16% samples (19/120) and included M. mucogenicum (nine), M. porcinum (three), M. avium (three), M. gordonae (one), M. cosmeticum (one), M. fortuitum (one), and Mycobacterium sp (one). All household water samples that contained NTM complied with the standards required to grade the water as "good quality" potable water.

Conclusion: Household potable water may be a potential source of NTM infection in Mexico City.

Figure 1

Household sampling sites (●), in Mexico City. Gustavo A. Madero borough (site 1), Miguel Hidalgo borough (site 2), Benito Juárez borough (site 3), Magdalena Contreras borough (site 4), Xochimilco borough (site 5). Sites 1 and 5 received groundwater from wells and sites 2, 3 and 4 received surface water from rivers (see also Table 1).

Figure 2

Number of positive-NTM samples per household.

Figure 3

Number of positive-NTM household water samples per month during November 2008 to October 2009.