Microbiological Quality and Presence of Clinically Relevant Nontuberculous Mycobacteria in Purified Water from Vending Machines in Michoacan, Mexico.

Abstract

In this study, 104 purified water samples were collected from vending machines in the three main cities of Michoacan, Mexico, to assess microbiological quality and the occurrence of diarrheagenic Escherichia coli pathotypes (DEP) and nontuberculous mycobacteria (NTM). Aerobic mesophilic bacteria were detected in all samples, with concentrations ranging from 0.95 to 3.71 log₁₀ CFU/mL. A total of 62, 34, and 25 samples tested positive for total coliforms, fecal coliforms, and E. coli, respectively. Sixty-two samples exceeded Mexico's official guideline. None of the 58 E. coli strains isolated from the 25 E. coli-positive samples belonged to DEP. NTM species were recovered from 47 samples, including M. mucogenicum (n = 18), M. abscessus (n = 11), M. chelonae (n = 7), M. porcinum (n = 3), M. fortuitum (n = 2), M. septicum (n = 1), M. phocaicum (n = 1), and M. brisbanense (n = 1). Three additional isolates could not be identified. All NTM strains produced biofilm and exhibited sliding motility. These findings highlight significant microbiological risks associated with vending machine water and underscore the need for manufacturers to ensure regular maintenance to provide safe and reliable purified water to consumers.