Waterborne Legionella bozemanii and nosocomial pneumonia in immunosuppressed patients.

From October 1983 to February 1984, five episodes of nosocomial pneumonia caused by Legionella bozemanii occurred in immunosuppressed patients at a 300-bed community hospital. Pulmonary infiltrates were predominantly patchy and present in multiple lobes and bilaterally; cavitation occurred in one patient. Patients responded promptly and completely to treatment with erythromycin and rifampin. Epidemiologic studies showed that all patients had been continuously or recently hospitalized at the same institution. Legionella bozemanii was cultured from four of the five infected patients, from tapwater in patient care areas, from the hospital's hotwater holding tank, and from soil in an area of excavation and new construction on hospital property. Chlorination and heat sterilization of the tank eliminated L. bozemanii from the water and no further cases were seen. This outbreak reaffirms that excavation and construction are risk factors for the outbreak of nosocomial legionella pneumonia and is the first description of nosocomial infection due to L. bozemanii.