Japanese Society for Infection Prevention and Control-Online Journal

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Contamination of Hot Water Supply System by Legionella Bacterium Found in Nosocomial Infection and Subsequent Countermeasures

Kenichi ISOME, Kayo NAKASHIMA, Mami IKEMACHI, Takashi YAMASAKI, Shinji NAKASAKO, Kazuya MIYAGAWA and Hiroshi EIZAWA
Kobe City Nishi-Kobe Medical Center Infection Control Office

Our hospital is a regional core hospital with 475 beds, and the 25-year-old building is a steel reinforced concrete structure with 1 floor underground and 10 floors above ground. A 79-year-old woman who had been treated with prednisolone 45 mg/day for Evans syndrome had a high fever on day 9 after prednisolone administration. She was diagnosed with Legionella pneumonia based on a lung consolidation on her chest X-ray with a positive urinary antigen for Legionella. Upon investigation of the water supply and hot water supply system on the suspicion of nosocomial Legionella infection, Legionella pneumophila serogroup 1 was detected in the hot water supply systems of all the wards on the 5^th-10^th floors. We then genotyped the Legionella from the patient and confirmed that the strain was the same as the L. pneumophila detected from the water supply system. To eliminate the nosocomial Legionella infections, we conducted hot water flushing and shower hose disinfection and replacement of all hot water taps and revised ward care restrictions. Then, we performed Legionella culture at 82 randomly selected locations after flushing and confirmed the absence of L. pneumophila, except one location where it was continuously detected due to the branched pipes that were not recognized and the flushing was not enough. We finally confirmed the absence of L. pneumophila after the flushing was carried throughout the pipes with the stagnated water. We also conducted follow-up surveys of patients who were discharged or transferred to other hospitals and health surveys for hospital staff. There was no new patient other than our patient; however, during the inspection to regularly monitor the Legionella contamination in the water supply system, L. pneumophila was detected again in a hot water tap that was used less frequently, which could be due to a contamination from biofilm. Our experience suggests that once L. pneumophila is detected from the water supply system, it is necessary to manage a long-term plan to eliminate the contamination that could persist due to biofilm formation in the pipes. Based on the experience, we established a manual for our hospital.

Key words：Legionella, nosocomial infections, hot water supply system, biofilm

e-mail: ken-ime＠mail.goo.ne.jp

Received: October 10, 2019
Accepted: January 6, 2020

35 (2)：81─86,2020