Isolation of Legionella pneumophila from water systems: methods and preliminary results.

A preliminary survey of water systems in hospitals and hotels showed that Legionella pneumophila may be found in water storage and distribution systems as well as in the recirculating cooling water of air-conditioning plants. Altogether 42 isolates of L pneumophila were made from 31 establishments, six of which were associated with cases of legionnaires' disease but in 25 of which there was no known association with disease. In the six establishments implicated epidemiologically as the source of legionnaires' disease, these organisms were found in each of their water-distribution systems and also in the cooling water from each of the three with cooling towers. In establishments not associated with cases, water from three out of nine cooling towers, four out of 24 taps or showers, and one out of 15 storage tanks was found to contain legionellae. The organisms were isolated by guinea-pig inoculation and subsequent culture of their peritoneal fluid, liver, and spleen. Finding L pneumophila in water systems in the absence of cases of legionnaires' disease should not at present be an indication for attempts at eradication.