Plumbing system shock absorbers as a source of Legionella pneumophila

Water distribution systems have been demonstrated to be a major source of nosocomial legionellosis. We describe an outbreak in our institution in which a novel source of Legionella pneumophila was identified in the plumbing system.

After an outbreak of 10 cases of legionellosis in our hospital, recommended measures including superheating of the hot water to 80 degrees C, hyperchlorination to 2 ppm, and flushing resulted in no new cases in the following 5 years. Recently, despite these control measures, three new cases occurred. Surveillance cultures of shower heads and water tanks were negative; cultures of tap water samples remained positive. This prompted a search for another reservoir. Shock absorbers installed within water pipes to decrease noise were suspected.

One hundred twenty-five shock absorbers were removed and cultured. A total of 13 (10%) yielded heavy growth of L. pneumophila (serogroup 1). Since their removal, no new cases have been found and the percentage of positive results of random tap water culture has dropped from 20% to 5%.

This is the first report that identifies shock absorbers as a possible reservoir for L. pneumophila. We recommend that institutions with endemic legionellosis assess the water system for possible removal of shock absorbers.