Relationship between Colonization of Building Water Systems by Legionella pneumophila and Environmental Factors

Abstract

Legionella species are widespread in aquatic environments. Legionella pneumophila is a pathogenic bacteria and is responsible for Legionnaires' disease. Man-made water systems are contaminated by legionellae through the municipal water supply. L. pneumophila is generally found in hot water systems and biofilms that are present in water supply systems and multiplies there within protozoan cells. Bacterial transmission to humans occurs through droplets generated from cooling towers, shower heads, and other man-made devices that generate aerosols. The relationship between L. pneumophila and total viable bacteria counts (22°C) was performed by linear regression. A cultural analysis of water systems of 139 hotels showed that 57 of the hotels (41%) were contaminated by L. pneumophila. L. pneumophila serogroup 1 was isolated from 29 (23.3%) water samples, whereas L. pneumophila serogroups 2 to 14 were isolated from 95 (76.6%) water samples. The mean water temperature varied from 15 to 62°C in cold and hot water samples. It was found that the effective growth temperature of L. pneumophila ranged from 28°C to 41°C. An epidemiologic case has been notified in one of the hotels surveyed in which L. pneumophila serogroup 1 was isolated.