title: Comparative effectiveness of cefazolin versus cloxacillin as definitive antibiotic therapy for MSSA bacteraemia: results from a large multicentre cohort study.
abstract: OBJECTIVE
  We compared the effectiveness of cefazolin versus cloxacillin in the treatment of MSSA bacteraemia in terms of mortality and relapse.
  
  
  METHODS
  A retrospective cohort study examined consecutive patients with Staphylococcus aureus bacteraemia from six academic and community hospitals between 2007 and 2010. Patients with MSSA bacteraemia who received cefazolin or cloxacillin as the predominant definitive antibiotic therapy were included in the study. Ninety-day mortality was compared between the two groups matched by propensity scores.
  
  
  RESULTS
  Of 354 patients included in the study, 105 (30%) received cefazolin and 249 (70%) received cloxacillin as the definitive antibiotic therapy. In 90 days, 96 (27%) patients died: 21/105 (20%) in the cefazolin group and 75/249 (30%) in the cloxacillin group. Within 90 days, 10 patients (3%) had a relapse of S. aureus infection: 6/105 (6%) in the cefazolin group and 4/249 (2%) in the cloxacillin group. All relapses in the cefazolin group were related to a deep-seated infection. Based on the estimated propensity score, 90 patients in the cefazolin group were matched with 90 patients in the cloxacillin group. In the propensity score-matched groups, cefazolin had an HR of 0.58 (95% CI 0.31-1.08, P = 0.0846) for 90 day mortality.
  
  
  CONCLUSIONS
  There was no significant clinical difference between cefazolin and cloxacillin in the treatment of MSSA bacteraemia with respect to mortality. Cefazolin was associated with non-significantly more relapses compared with cloxacillin, especially in deep-seated S. aureus infections.
authors.affiliation: Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Bai
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Showler
authors.affiliation: Mount Sinai Hospital, Toronto, Ontario, Canada Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Burry
authors.affiliation: Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Steinberg
authors.affiliation: Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada Lakeridge Health, Oshawa, Ontario, Canada.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Ricciuto
authors.affiliation: Trillium Health Partners, Mississauga, Ontario, Canada.
authors.forename: Tania
authors.initials: T
authors.lastname: Fernandes
authors.affiliation: Trillium Health Partners, Mississauga, Ontario, Canada.
authors.forename: Anna
authors.initials: A
authors.lastname: Chiu
authors.affiliation: North York General Hospital, Toronto, Ontario, Canada.
authors.forename: Sumit
authors.initials: S
authors.lastname: Raybardhan
authors.affiliation: Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Science
authors.affiliation: Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Eshan
authors.initials: E
authors.lastname: Fernando
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Tomlinson
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada Mount Sinai Hospital, Toronto, Ontario, Canada Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Chaim M
authors.initials: CM
authors.lastname: Bell
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada Division of Infectious Diseases, University of Toronto, Toronto, Ontario, Canada Mount Sinai Hospital, Toronto, Ontario, Canada amorris@mtsinai.on.ca.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Morris
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D002437:Cefazolin / Q000627:therapeutic use*; D003023:Cloxacillin / Q000627:therapeutic use*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D013211:Staphylococcus aureus / Q000187:drug effects*; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D002437:Cefazolin; D003023:Cloxacillin
keywords: S. aureus; Staphylococcus aureus; bloodstream infections