title: Molecular epidemiology of Legionella pneumophila infection at a Canadian tertiary care institution.
abstract: OBJECTIVE
  To characterize the molecular epidemiology of Legionella species infection at one Canadian tertiary care centre.
  
  
  METHODS
  Twenty-eight clinical isolates and 12 environmental isolates obtained over a six-year period were analyzed by restriction fragment length polymorphism (rflp) of chromosomal dna. Isolates included 15 from 12 patients with hospital acquired illness and 13 from nine patients with community acquired infection.
  
  
  RESULTS
  One nosocomial strain was Legionella micdadei and one community strain was Legionella pneumophila serotype 6; all others were L pneumophila serotype 1. rflp typing revealed one clone for all cases of a 1985 single-ward outbreak and five of six nonoutbreak L pneumophila nosocomial cases. An rflp pattern identical or highly related to that of the nosocomial clonal type was noted among nine of 12 L pneumophila serotype 1 community isolates. The remaining three isolates had two related rflp patterns distinct from the institutional strain. The nosocomial and community strains were isolated from multiple institutional water samples in the institution. For the environmental isolates, monoclonal antibody typing was more discriminating than rflp typing: seven monoclonal antibody subtypes were distinguished among 12 environmental isolates comprising three distinct rflp patterns.
  
  
  CONCLUSIONS
  Despite multiple L pneumophila serotype 1 strains isolated in the authors' institutional water, a single clone of L pneumophila produced most disease. Community acquired disease was caused by a wider variety of strains.
authors.affiliation: Section of Infectious Diseases, Departments of Medicine and Medical Microbiology, University of Manitoba; Infection Control Unit and Clinical Microbiology Laboratory, Health Sciences Centre; Cadham Provincial Laboratory, Winnipeg, Manitoba; Department of Microbiology and Infectious Diseases, St Joseph's Health Centre; and Department of Microbiology and Immunology, University of Western Ontario, London, Ontario.
authors.forename: L
authors.initials: L
authors.lastname: Nicolle
authors.forename: H
authors.initials: H
authors.lastname: Bialkowska-Hobrzanska
authors.forename: B
authors.initials: B
authors.lastname: Dyck
authors.forename: L
authors.initials: L
authors.lastname: Sekla
authors.forename: S
authors.initials: S
authors.lastname: Parker