title: Persistence of Legionella pneumophila in a hospital's water system: a 13-year survey.
abstract: OBJECTIVE
  To describe the molecular epidemiology of Legionella pneumophila infections in the University of Iowa Hospitals and Clinics (UIHC).
  
  
  METHODS
  Molecular epidemiological study using pulsed-field gel electrophoresis (PFGE).
  
  
  METHODS
  A large university teaching hospital. ISOLATES: All surviving isolates obtained from culture-proven nosocomial L. pneumophila infections 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 of L. pneumophila pneumonia 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.
  
  
  CONCLUSIONS
  Specific strains of L. pneumophila can colonize hospital water supplies and cause nosocomial infections over long periods of time.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242-1081, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Rangel-Frausto
authors.forename: P
authors.initials: P
authors.lastname: Rhomberg
authors.forename: R J
authors.initials: RJ
authors.lastname: Hollis
authors.forename: M A
authors.initials: MA
authors.lastname: Pfaller
authors.forename: R P
authors.initials: RP
authors.lastname: Wenzel
authors.forename: C M
authors.initials: CM
authors.lastname: Helms
authors.forename: L A
authors.initials: LA
authors.lastname: Herwaldt
mesh_terms: D003428:Cross Infection / Q000382:microbiology* / Q000517:prevention & control; D016521:Electrophoresis, Gel, Pulsed-Field; D006785:Hospitals, University; D006801:Humans; D017053:Infection Control; D007484:Iowa; D016952:Legionella pneumophila / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000382:microbiology* / Q000517:prevention & control / Q000635:transmission; D014871:Water Microbiology; D014881:Water Supply