title: Comparison of outcomes in patients with methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia who are treated with β-lactam vs vancomycin empiric therapy: a retrospective cohort study.
abstract: Prior studies suggested that vancomycin may be inferior to β-lactams for the empiric treatment of methicillin-susceptible S. aureus (MSSA) bacteremia. We assessed whether empiric therapy with β-lactams compared to vancomycin was associated with differences in clinical outcomes in patients with MSSA bacteremia.
  
  
  
  We conducted a retrospective cohort study of adult inpatients with their first episode of MSSA bacteremia at two tertiary care hospitals in Vancouver, Canada, between 2007 and 2014. Exposure was either empiric β-lactam or vancomycin therapy. All patients received definitive treatment with cloxacillin or cefazolin. The primary outcome was 28-day mortality. Secondary outcomes were 90-day mortality, recurrent infection at 6 months, duration of bacteremia and hospital length-of-stay. Outcomes were adjusted using multivariable logistic regression.
  
  
  
  Of 814 patients identified, 400 met inclusion criteria (β-lactam = 200, vancomycin = 200). Overall 28-day mortality was 8.5 % (n=34). There were more cases of infective endocarditis in the β-lactam than in the vancomycin group [45 (22.5 %) vs 23 (11.5 %), p < 0.01]. Adjusted mortality at 28 days was similar between the two groups (OR: 1.14; 95 % CI: 0.49-2.64). No differences in secondary outcomes were observed. Transition to cloxacillin or cefazolin occurred within a median of 67.8 h in the vancomycin group.
  
  
  
  Empiric therapy with β-lactams was not associated with differences in all-cause mortality, recurrent infection, microbiological cure or hospital length-of-stay compared to vancomycin. Vancomycin monotherapy may be appropriate for the empiric treatment of MSSA bacteremia if definitive therapy with cloxacillin or cefazolin can be initiated within 3 days.
authors.affiliation: PGY-V Infectious Diseases Residency Training Program, University of British Columbia, Vancouver General Hospital, D 452 Heather Pavilion, 2733 Heather Street, Vancouver, BC, V5Z 1 M9, Canada. wongdavi@mail.ubc.ca.
authors.forename: Davie
authors.initials: D
authors.lastname: Wong
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.|Division of Medical Microbiology and Infection Control, Vancouver General Hospital, JPPN1, Medical Microbiology Laboratory, 899 W 12th Ave, Vancouver, BC, V5Z 1 M9, Canada.
authors.forename: Titus
authors.initials: T
authors.lastname: Wong
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.|Division of Medical Microbiology, St. Paul's Hospital, Medical Microbiology Laboratory, 1081 Burrard St., Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Marc
authors.initials: M
authors.lastname: Romney
authors.affiliation: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.|Division of Medical Microbiology, St. Paul's Hospital, Medical Microbiology Laboratory, 1081 Burrard St., Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Victor
authors.initials: V
authors.lastname: Leung
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D002170:Canada; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D013211:Staphylococcus aureus / Q000187:drug effects; D016896:Treatment Outcome; D014640:Vancomycin / Q000494:pharmacology / Q000627:therapeutic use*; D047090:beta-Lactams / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D014640:Vancomycin
keywords: Bacteremia; Beta-lactam; Empiric; Staphylococcus aureus; Therapy; Vancomycin