Objective: Report of the technical, microbiological and epidemiological investigation following 2 cases of fatal Legionella pneumonia.
Design: Descriptive.
Method: Faced with 2 nosocomial cases in a rehabilitation centre in the South of Limburg, the Netherlands, the water supply was investigated. Water temperatures from different taps were measured. Legionella cultures were made from respiratory patients' specimens, water samples and smears from all mixing taps (used in showers), samples from hot and cold water taps from the infected ward and from the five other wards. The strains were typed by serotyping and polymerase chain reaction.
Results: The circulating cold water sometimes warmed up to 40 degrees C (within the Legionella growth range). From the sputum of the 2 male patients with rheumatoid arthritis who died of Legionella pneumonia the same Legionella pneumophila (serotype I) was cultured as from the water supply. Of the showers on the contaminated ward 19% (12/63) were positive for Legionella as were 59% (35/59) of the cold water taps. Cultures from the hot water supply were negative just like control cultures from five other wards and swabs from showerheads and hoses. The cold water tubes ran next to the hot water tubes and the central heating system in the same shaft. On the infected ward patients were absent during the weekends. As one of the subsequent measures, the cold water pipes were relocated to another shaft.
Conclusion: The combination of an elevated cold water temperature caused by heating along a distance by nearby hot water and heating piping and the regular stasis of water during the weekends when the ward was closed, most probably stimulated the multiplication of Legionella in the water supply. In order to minimize contamination of cold water its temperature must be kept below 20 degrees C. Surveillance of intramural water systems is necessary to prevent nosocomial infections.