Legionella infection risk from domestic hot water

We investigated Legionellaand Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy. Chemical parameters (hardness, free chlorine, and trace elements) were determined. Legionellaspp. were detected in 33 (22.6%) and Pseudomonas spp. in 56 (38.4%) of 146 samples. Some factors associated with Legionellacontamination were heater type, tank distance and capacity, water plant age, and mineral content. Pseudomonaspresence was influenced by water source, hardness, free chlorine, and temperature. Legionellacontamination was associated with a centralized heater, distance from the heater point >10 m, and a water plant >10 years old. Furthermore, zinc levels of <20 mg/Land copper levels of >50 mg/L appeared to be protective against Legionellacolonization. Legionellaspecies and serogroups were differently distributed according to heater type, water temperature, and free chlorine, suggesting that Legionella strains may have a different sensibility and resistance to environmental factors and different ecologic niches