Abstract
We investigated Legionella and Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy. Chemical parameters (hardness, free chlorine, and trace elements) were determined. Legionella spp. were detected in 33 (22.6%) and Pseudomonas spp. in 56 (38.4%) of 146 samples. Some factors associated with Legionella contamination were heater type, tank distance and capacity, water plant age, and mineral content. Pseudomonas presence was influenced by water source, hardness, free chlorine, and temperature. Legionella contamination 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 μg/L and copper levels of >50 μg/L appeared to be protective against Legionella colonization. Legionella species 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.
Highlights
We investigated Legionella and Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy
Little is known about sporadically occurring cases of community-acquired legionellosis, which accounts for most infections [7,8], correlation analyses suggest that a substantial proportion of these cases may be residentially acquired and associated with bacteria in hot water distribution systems [9]
To neutralize residual free chlorine, sodium thiosulphate was added in sterile bottles for bacteriologic analysis, whereas acid-preserved glass bottles were used for chemical determinations
Summary
We investigated Legionella and Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy. A central heating system, distance from heating point >10 m, and a system >10 years old were each independently associated with higher risk of Legionella colonization, whereas water with levels of copper >50 μg/L and zinc
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