Endemicity of Legionella pneumophila serogroup 3 in a hospital water supply

Abstract A microbiological and epidemiological investigation at the Infectious Diseases Hospital in Turin, Italy, demonstrated Legionella pneumophila serogroup 3 at 10 2 to > 4 × 10 3 cfu l −1 from 24 of 32 hot water samples collected from hand-basins in six separate buildings. A sample taken from the public water supply, and a hot water sample (80 °C) collected from hot water tanks, did not yield legionellas. Legionella pneumophila serogroup 3 was found in samples taken at the first point of mixed hot and cold water (50 °C) at 3 × 10 2 cfu l −1 . 12 of 26 samples from the shower-heads yielded 10 3 to 2·5 × 10 5 cfu l −1 and one of 12 water samples from oxygen bubble humidifiers tested yielded 1·6 × 10 4 cfu l −1 . No other legionellas species or serogroups of Legionella pneumophila were isolated during the study. No cases of nosocomial pneumonia were detected among 3653 patients' records, nor was there serological evidence of Legionella infection in the 180 patients tested.