Search for acid-fast bacilli in bottled mineral waters.

Samples of bottled mineral water sold in Italy in accordance with the law on microbiological standards were examined for the presence of acid-fast bacilli. Eighty-four samples were tested, 11 with added carbon dioxide and 73 without. Acid-fast bacilli were found in 1 of the former samples and in 8 of the latter, a total of 10.7%. The mycobacterial count was always very low (2-3 cfu/litre) except for one sample which showed large numbers of Mycobacterium sphagni. This finding was not confirmed in two following samplings of the same water. The other acid-fast bacilli isolated were: M. gordonae (four strains), M. flavescens (one strain), M. phlei (one strain) and Nocardia sp. (two strains) in two samples of different water. These bacilli are not thought to be a normal component of the waters but are the result of incidental contamination. The risk of infection from drinking such waters can be regarded as irrelevant in hospitalized or immunologically compromised subjects who fact a greater risk when using tap water for drinking or washing.