[Microbiological evaluation of risk of legionellosis and practical methods applied for elimination of Legionella pneumophila from hospital water systems].

Microbiological evaluation of risk of legionellosis was based on the results of water samples collected from hospital water systems examinations. The percentage of positive water samples, number of detected Legionella spp. cfu/100ml, determined serogroup and subgroup of isolated strains as well as genetic virulence markers (rtxA, mompS) were analyzed by multivariable regression tests. The ability to adhere to cells A549 and proliferate in THP-1 cells were also examined. Strong correlation was found between the detected number of Legionella spp. cells (cfu/100ml) and percentage of positive samples, presence of gene depending ability bacteria to move, adhere to A549 cells and presence of mompS gene for special protein building capsule. From other side, correlation between identified cases or infections due to L. pneumophila and presence of gene: rtxA, mompS, and epitop MAb3/l was determined. In conclusion it was indicated that evaluation of risk of legionellosis should be based on ability the legionellae strains to prolify, and grow in water systems and also on virulence properties of isolated strains, especially those producing RTX toxin, flagella and presenting virulence epitop MAb3/l. Two examples of practical application methods for reduction of risk of nosocomial infection were described also. It was shown that cooperation of engineers and microbiologist is essential for effective elimination of Legionella from water systems and reduction of the risk of Legionella infection in hospital.