Isolation of Legionella pneumophila from hospital shower heads

Legionella pneumophila serogroup 6 was isolated from nine of 16 shower heads in a Chicago hospital ward where three patients had contracted Legionnaires' disease caused by serogroup 6 L. pneumophila. Each patient had showered there 2 to 10 days before the onset of disease symptoms. We also isolated the bacteria in two other hospitals, and found the same serogroups as had been causing Legionnaires' disease in those hospitals: serogroup 1 in Pittsburgh and serogroups 1 and 4 in Los Angeles. However, showers from hospital wards where no patients had contracted Legionnaires' disease also yielded L. pneumophila. Shower heads at the Chicago hospital were sterilized with ethylene oxide but rapidly became recontaminated, suggesting that the potable water at these hospitals may have contained the organism. The question of whether aerosols of shower water or other exposures to potable water containing L. pneumophila may cause nosocomial Legionnaires' disease has not been resolved but deserves further study.