title: Infection with transmissible strains of Pseudomonas aeruginosa and clinical outcomes in adults with cystic fibrosis.
abstract: BACKGROUND
  Studies from Australia and the United Kingdom have shown that some patients with cystic fibrosis are infected with common transmissible strains of Pseudomonas aeruginosa.
  
  
  OBJECTIVE
  To determine the prevalence and incidence of infection with transmissible strains of P. aeruginosa and whether presence of the organism was associated with adverse clinical outcomes in Canada.
  
  
  METHODS
  Prospective observational cohort study of adult patients cared for at cystic fibrosis clinics in Ontario, Canada, with enrollment from September 2005 to September 2008. Sputum was collected at baseline, 3 months, and yearly thereafter for 3 years; and retrieved P. aeruginosa isolates were genotyped. Vital status (death or lung transplant) was assessed for all enrolled patients until December 31, 2009.
  
  
  METHODS
  Incidence and prevalence of P. aeruginosa isolation, rates of decline in lung function, and time to death or lung transplantation.
  
  
  RESULTS
  Of the 446 patients with cystic fibrosis studied, 102 were discovered to be infected with 1 of 2 common transmissible strains of P. aeruginosa at study entry. Sixty-seven patients were infected with strain A (15%), 32 were infected with strain B (7%), and 3 were simultaneously infected with both strains (0.6%). Strain A was found to be genetically identical to the Liverpool epidemic strain but strain B has not been previously described as an epidemic strain. The incidence rate of new infections with these 2 transmissible strains was relatively low (7.0 per 1000 person-years; 95% confidence interval [CI], 1.8-12.2 per 1000 person-years). Compared with patients infected with unique strains of P. aeruginosa, patients infected with the Liverpool epidemic strain (strain A) and strain B had similar declines in lung function (difference in decline in percent predicted forced expiratory volume in the first second of expiration of 0.64% per year [95% CI, -1.52% to 2.80% per year] and 1.66% per year [95% CI, -1.00% to 4.30%], respectively). However, the 3-year rate of death or lung transplantation was greater in those infected with the Liverpool epidemic strain (18.6%) compared with those infected with unique strains (8.7%) (adjusted hazard ratio, 3.26 [95% CI, 1.41 to 7.54]; P = .01).
  
  
  CONCLUSIONS
  A common strain of P. aeruginosa (Liverpool epidemic strain/strain A) infects patients with cystic fibrosis in Canada and the United Kingdom. Infection with this strain in adult Canadian patients with cystic fibrosis was associated with a greater risk of death or lung transplantation.
authors.affiliation: Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada, K1H 8L6. saaron@ohri.ca
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Aaron
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Vandemheen
authors.forename: Karam
authors.initials: K
authors.lastname: Ramotar
authors.forename: Tracy
authors.initials: T
authors.lastname: Giesbrecht-Lewis
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Tullis
authors.forename: Andreas
authors.initials: A
authors.lastname: Freitag
authors.forename: Nigel
authors.initials: N
authors.lastname: Paterson
authors.forename: Mary
authors.initials: M
authors.lastname: Jackson
authors.forename: M Diane
authors.initials: MD
authors.lastname: Lougheed
authors.forename: Christopher
authors.initials: C
authors.lastname: Dowson
authors.forename: Vijay
authors.initials: V
authors.lastname: Kumar
authors.forename: Wendy
authors.initials: W
authors.lastname: Ferris
authors.forename: Francis
authors.initials: F
authors.lastname: Chan
authors.forename: Steve
authors.initials: S
authors.lastname: Doucette
authors.forename: Dean
authors.initials: D
authors.lastname: Fergusson
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003550:Cystic Fibrosis / Q000150:complications* / Q000382:microbiology*; D005260:Female; D006801:Humans; D015994:Incidence; D016040:Lung Transplantation; D008297:Male; D009864:Ontario / Q000453:epidemiology; D015995:Prevalence; D011552:Pseudomonas Infections / Q000453:epidemiology* / Q000635:transmission; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D012307:Risk Factors; D016019:Survival Analysis; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult