Nontuberculous mycobacteria (NTM) are ubiquitous and have been isolated from a variety of environmental sources, including water. Various NTM were isolated from biofilms in drinking water distribution systems in two urban and two semiurban areas in South Africa. Most of the isolates belonged to opportunistic pathogenic species of the NTM group, but none belonged to the Mycobacterium avium complex.The genus Mycobacterium comprises both the strictly pathogenic species that are transmitted by human or animal reservoirs only (M. tuberculosis, M. leprae) and the so-called nontuberculous mycobacteria (NTM) (3,13,14). The NTM have generally been associated with soil and water, and while many of them are considered to be nonpathogenic, an increasing number are being reported as opportunistic pathogens (3,5,16). This growing number of atypical pathogenic mycobacteria includes M. abscessus (8), M. chelonae (10), M. fortuitum (16,27), M. gordonae (19), M. mageritense (9), and M. xenopi (5). Several NTM constitute a risk not only to immunosuppressed persons but also to otherwise healthy persons (10). They can cause pulmonary and cutaneous diseases, lymphadenitis, and other infections (14).M. abscessus, M. gilvum, M. gordonae, and M. mageritense have been associated with municipal water supplies (7,9,12). In a recent report, furunculosis, caused by M. mageritense, was also linked to the water supply of a salon where two women received footbaths (9). In another report, cervical lymphadenitis in children below 2 years of age has been linked with mycobacteria in the United States, the United Kingdom, and Australia (21). These infections were linked to the prevalence of M. avium and M. scrofulaceum in water (21). There are also reports that NTM can be present in aerosols, such as at swimming pools and spas, of water that may contain mycobacteria and that individuals exposed to the aerosols for extended periods are more at risk of contracting an infection (6). In the United States alone, over a million workers are exposed to aerosols generated by metal grinding, and exposure to such aerosols can lead to hypersensitivity, pneumonitis, and chronic obstructive pulmonary disease (6, 21).NTM are tolerant to a much wider pH and temperature range than are most other bacterial pathogens detected in municipal water supplies. They are also generally tolerant to chlorine, making them potentially more difficult to eliminate (12, 13). Adding to this is their ability to form biofilms on surfaces in drinking water distribution systems (12, 24). The growth of NTM in biofilms may lead to dissemination into the bulk water, constituting a risk to consumers both by drinking and by inhalation of aerosols though showering and swimming.NTM can form biofilms under low-nutrient conditions, making surfaces of drinking water distribution systems an environment for their growth and possible dissemination (12). The aim of this study was to determine the presence and diversity of NTM in biofilms in drinking water distribution systems by analyzing samples from...

Water for human consumption is required to be free from any bacteria that might pose a health risk. The presence of biofilms in the drinking water distribution system may play a role in the presence of potential pathogens in the drinking water supply. Ninety-five biofilm samples from various parts of South Africa were tested for the presence of Escherichia coli, Aeromonas, Pseudomonas, Salmonella, Shigella and Vibrio spp. Members of these genera were quantified by the three-tube most probable number (MPN) approach using enrichment broths and plating on selective agars. The heterotrophic culturable counts were determined for both the planktonic and biofilm phases of the samples. Biofilm density varied between 10 and 1.9 x 10(9) colony forming units cm(-2). The 16S rRNA identity of the putative pathogenic isolates revealed that high numbers of Aeromonas, Pseudomonas, Klebsiella and Enterobacter were present, but no putative Salmonella and Shigella could be confirmed. None of the Pseudomonas isolates belonged to the pathogenic Pseudomonas aeruginosa or Pseudomonas mendocina while the Aeromonas isolates showed relatedness to known pathogenic members of this group.