Nosocomial legionellosis associated with use of oxygen bubble humidifiers and underwater chest drains

In 1 year 12 of 48 patients who developed fatal pneumonia following admission with non-respiratory disorders to the Hospital Molinette, Torino, yielded Legionella pneumophila serogroup 1 from lung at autopsy. Patients were hospitalized on seven different wards for different conditions; only two of the wards had air conditioning but legionellas were not isolated from these. All patients were in poor health or immunocompromised. Some patients had inhaled humidified oxygen from piped supplies and three had undergone surgery. Legionella pneumophila serogroup 1 was detected in the water of oxygen bubble humidifiers and an underwater chest drain. The contaminated devices had been filled with tap or distilled water and the hospital water supply was found to be contaminated with L. pneumophila serogroup 1. Our findings suggest that filling bubble humidifiers or underwater chest drains with tap water is a potential hazard and should be avoided.