E . L EO N I, P. L EG NA N I, M. T . M UC C I A ND R . P IR A NI . 1999. A study was performed to evaluate the prevalence of non-tubercular mycobacteria in swimming pool environments. The bacteria in question were found in 88·2% of pool water samples. The most frequent species were Mycobacterium gordonae (73·5% of samples; range 1-840 cfu 100 ml −1 ), M. chelonei (38·2%; 2-360 cfu 100 ml −1 ) and M. fortuitum (35·3%; 2-250 cfu 100 ml −1 ). The same species were also recovered from the water at the different phases of the treatment cycle, with relative percentages similar to those of the pool water. Shower floors and pool edges also presented high concentrations of the mycobacteria (100% of samples) and M. marinum was isolated from the surfaces of pool edges on two occasions (4·5% of samples). The swimming pool environment provides a suitable habitat for the survival and reproduction of mycobacteria. Although mycobacteria are common in swimming pools, human mycobacterial disease associated with their use is rare. Apart from superficial infections with M. marinum, the risk of more serious diseases in subjects with weakened immune systems should not be underestimated, given the widespread presence of mycobacteria that are possible opportunistic pathogens and the direct contact bathers have with the water and aerosol.

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