title: Risk factors for Staphylococcus aureus surgical site infection during an outbreak in patients undergoing cardiovascular surgery.
abstract: BACKGROUND
  This study examined the epidemiology of an outbreak of Staphylococcus aureus surgical site infections (SSI) after cardiovascular surgery, and analyzed risk factors for S aureus SSIs.
  
  
  METHODS
  This was a retrospective case-control study to determine risk factors for S aureus SSI in 38 patients who developed S aureus SSI during the outbreak period, compared with age-, sex-, and procedure-matched controls. S aureus strains were typed by pulsed-field gel electrophoresis.
  
  
  RESULTS
  A total of 38 patients had S aureus SSI. Pulsed-field gel electrophoresis identified transmission of 3 S aureus clones (2 MSSA clones and 1 MRSA clone). Twenty-one health care workers were carriers of outbreak strains. In multivariate analysis, the significant risk factors for S aureus SSI were previous cardiac surgery (odds ratio, 7.41; 95% confidence interval, 1.05-52.16) and long procedure duration (odds ratio, 1.49; 95% confidence interval, 1.00-2.21).
  
  
  CONCLUSIONS
  This outbreak demonstrates evidence of nosocomial transmission of 3 clones of S aureus in the setting of incomplete compliance with recommended standard perioperative infection control measures, associated with a high prevalence of staff carriage of the predominant outbreak strains.
authors.affiliation: Department of Microbiology, University of Toronto, Toronto, ON, Canada. Manal.tadros@utoronto.ca
authors.forename: Manal A
authors.initials: MA
authors.lastname: Tadros
authors.forename: Victoria R
authors.initials: VR
authors.lastname: Williams
authors.forename: Suzanne
authors.initials: S
authors.lastname: Plourde
authors.forename: Sandra
authors.initials: S
authors.lastname: Callery
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Simor
authors.forename: Mary
authors.initials: M
authors.lastname: Vearncombe
mesh_terms: D000368:Aged; D002170:Canada / Q000453:epidemiology; D013504:Cardiovascular Surgical Procedures / Q000009:adverse effects / Q000706:statistics & numerical data; D016022:Case-Control Studies; D015984:Causality; D003428:Cross Infection / Q000453:epidemiology* / Q000517:prevention & control*; D004196:Disease Outbreaks / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000517:prevention & control; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000382:microbiology