Persistence ofLegionella Pneumophilain a Hospital's Water System: A 13-Year Survey

Abstract

AbstractObjective:To describe the molecular epidemiology ofLegionella pneumophilainfections in the University of Iowa Hospitals and Clinics (UIHC).Design:Molecular epidemiological study using pulsed-field gel electrophoresis (PFGE).Setting:A large university teaching hospital.Isolates:All surviving isolates obtained from culture-proven nosocomialL pneumophilainfections and all surviving isolates obtained from the University of Iowa Hospital and Clinics' water supply between 1981 and 1993.Results:Thirty-three isolates from culture-proven nosocomial cases ofL pneumophilapneumonia were available for typing. PFGE of genomic DNA from the clinical isolates identified six different strains. However, only strain C (16 cases) and strain D (13 cases) caused more than 1 case. Strain C caused clusters of nosocomial infection in 1981, 1986, and 1993 and also caused 4 sporadic cases. Strain D caused a cluster in 1987 and 1988 plus 4 sporadic cases. Of the six strains causing clinical infections, only strains C and D were identified in water samples. PFGE identified three strains in the water supply, of which strains C and D caused clinical disease and also persisted in the water supply during most of the study period.Conclusion:Specific strains ofL pneumophilacan colonize hospital water supplies and cause nosocomial infections over long periods of time.