Jpn. J. Infect. Dis., 60 (1), 5-9, 2007

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Original Article

Prospective Monitoring Study: Isolating Legionella pneumophila in a Hospital Water System Located in the Obstetrics and Gynecology Ward after Eradication of Legionella anisa and Reconstruction of Shower Units

Michio Koide1,4*, Tomoko Owan 2,4, Chikara Nakasone1, Natsuo Yamamoto 1, Shusaku Haranaga1,4, Futoshi Higa1,4, Masao Tateyama1,4, Nobuhisa Yamane3,4and Jiro Fujita1,4

1Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases (First Department of Internal Medicine), 2Department of Fundamental Nursing, 3Department of Clinical Laboratories, and 4Infection Control Room, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan

(Received June 12, 2006. Accepted October 19, 2006)


*Corresponding author: Mailing address: Department of Medicine and Therapeutics, Control and Prevention of Infectious Diseases (First Department of Internal Medicine), Faculty of Medicine, University of the Ryukyus, 207 Uehara, Nishihara-cho, Okinawa 903-0215, Japan. Tel: +81-98-895-1144, Fax: +81-98-895-1414,E-mail: koide-mi@med.u-ryukyu.ac.jp


SUMMARY: We previously reported on the sporadic contamination by Legionella anisa of shower units and sink taps at Ryukyu University Hospital. Starting in July 2003, the neonatal area underwent an 8-month reconstruction, and in March 2005, the boiler system was replaced. We therefore examined shower water and tap water for the presence of Legionella just after replacement of the boiler system. In 3 of the 8 water samples collected from the remodeled area, we isolated Legionella pneumophila serogroup 1 and L. anisa. Moreover, L. pneumophila serogroup 1 was isolated in 4 of the 5 water samples gathered from the unreconstructed area of the same floor. Random amplified polymorphic DNA analysis suggested that a single clone of L. pneumophila might exist throughout the floors of the water distribution system. We replaced the shower units at the Legionella-positive site, and began flushing the sink-faucets with water heated to 55℃ for at least 1 h every morning. As a result, Legionella was not subsequently isolated in water samples. In this prospective study, we identified a central contamination by L. pneumophila serogroup 1 and showed that flushing with hot tap water was effective to counter this situation.


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