Non-tuberculous mycobacteria, amoebae and bacterial indicators in swimming pool and spa.

Abstract Non-tuberculous mycobacteria are microorganisms commonly living in the environment. Nevertheless, most of them are opportunistic pathogens. To verify their concentrations in swimming pool and spa, analyses were performed on water and biofilm samples and the data were correlated to the global microbiological quality of water. The 93% of samples were found positive for the investigated bacteria. All water samples were positive for mycobacteria with higher densities in the whirlpool (10 5  cfu/L). Swimming pool samples showed variable counts ranging from 29 to 7 × 10 4  cfu/L while similar levels of mycobacteria (around to 10 2  cfu/L) characterized water samples from the spa. The 80% of the biofilm samples were positive and one of them was characterized by very high densities (3.7 × 10 3  cfu/cm 2 ). The most frequently isolated species was Mycobacterium mucogenicum followed by Mycobacterium immunogenum . Free-living amoebae were never detected in swimming pools and in the whirlpool, while they were found in 75% of spa samples and in 67% of biofilm samples. The mean values of heterotrophic bacteria in swimming pool water were similar to those observed in spa water at both temperatures. Higher values were detected in the whirlpool. Microbial indicators of fecal contamination, Staphylococcus aureus and Pseudomonas aeruginosa were never detected both in water and in biofilm samples. No correlation exists between the monitoring controls carried out by law and the occurrence of mycobacteria that may represent a potential risk in facilities such as those investigated.