Legionella contamination in hot water of Italian hotels

Paola Borella, Maria Teresa Montagna, Serena Stampi, Giovanna Stancanelli, Vincenzo Romano-Spica, Maria Triassi, Isabella Marchesi, Annalisa Bargellini, Daniela Tatò, Christian Napoli, Franca Zanetti, Erica Leoni, Matteo Moro, Stefania Scaltriti, Gabriella Ribera D'Alcalà, Rosalba Santarpia, Stefania Boccia

Research output: Contribution to journalArticlepeer-review


A cross-sectional multicenter survey of Italian hotels was conducted to investigate Legionella spp. contamination of hot water. Chemical parameters (hardness, free chlorine concentration, and trace element concentrations), water systems, and building characteristics were evaluated to study risk factors for colonization. The hot water systems of Italian hotels were strongly colonized by Legionella; 75% of the buildings examined and 60% of the water samples were contaminated, mainly at levels of ≥103 CFU liter-1, and Legionella pneumophila was the most frequently isolated species (87%). L. pneumophila serogroup 1 was isolated from 45.8% of the contaminated sites and from 32.5% of the hotels examined. When a multivariate logistic model was used, only hotel age was associated with contamination, but the risk factors differed depending on the contaminating species and serogroup. Soft water with higher chlorine levels and higher temperatures were associated with L. pneumophila serogroup 1 colonization, whereas the opposite was observed for serogroups 2 to 14. In conclusion, Italian hotels, particularly those located in old buildings, represent a major source of risk for Legionnaires' disease due to the high frequency of Legionella contamination, high germ concentration, and major L. pneumophila serogroup 1 colonization. The possible role of chlorine in favoring the survival of Legionella species is discussed.

Original languageEnglish
Pages (from-to)5805-5813
Number of pages9
JournalApplied and Environmental Microbiology
Issue number10
Publication statusPublished - Oct 2005

ASJC Scopus subject areas

  • Environmental Science(all)
  • Biotechnology
  • Microbiology

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