Nosocomial legionella pneumonia: demonstration of potable water as the source of infection

Abstract

SUMMARYFrom January 1983 until December 1985, 35 cases of sporadic nosocomial legionella pneumonia, all caused byLegionella pneumophila, were diagnosed in a university hospital.L. pneumophilaserogroup (SG) 1 was cultured from 12 of the 35 cases and compared to correspondingL. pneumophilaSG 1 isolates from water outlets in the patients' immediate environment by subtyping with monoclonal antibodies. The corresponding environmental isolates were identical to 9 out of 12 (75%) of those from the cases. However, even in the remaining three cases identical subtypes were found distributed throughout the hospital water supply. From the hospital water supply four different subtypes ofL. pneumophilaSG 1 were isolated, three of which were implicated in legionella pneumonia. Of 453 water samples taken during the study 298 (65.8%) were positive for legionellae. Species ofLegionellaother thanL. pneumophilahave not been isolated. This may explain the exclusiveness ofL.pneumophilaas the legionella pneumonia-causing agent. Our results suggest that the water supply system was the source of infection.