title: Comparative effectiveness of beta-lactams versus vancomycin for treatment of methicillin-susceptible Staphylococcus aureus bloodstream infections among 122 hospitals.
abstract: BACKGROUND
  Previous studies indicate that vancomycin is inferior to beta-lactams for treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bloodstream infections. However, it is unclear if this association is true for empiric and definitive therapy. Here, we compared beta-lactams with vancomycin for empiric and definitive therapy of MSSA bloodstream infections among patients admitted to 122 hospitals.
  
  
  METHODS
  This retrospective cohort study included all patients admitted to Veterans Affairs hospitals from 2003 to 2010 who had positive blood cultures for MSSA. Hazard ratios (HR) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression. Empiric therapy was defined as starting treatment 2 days before and up to 4 days after the first MSSA blood culture was collected. Definitive therapy was defined as starting treatment between 4 and 14 days after the first positive blood culture was collected.
  
  
  RESULTS
  Patients who received empiric therapy with a beta-lactam had similar mortality compared with those who received vancomycin (HR, 1.03; 95% CI, .89-1.20) after adjusting for other factors. However, patients who received definitive therapy with a beta-lactam had 35% lower mortality compared with patients who received vancomycin (HR, 0.65; 95% CI, .52-.80) after controlling for other factors. The hazard of mortality decreased further for patients who received cefazolin or antistaphylococcal penicillins compared with vancomycin (HR, 0.57; 95% CI, .46-.71).
  
  
  CONCLUSIONS
  For patients with MSSA bloodstream infections, beta-lactams are superior to vancomycin for definitive therapy but not for empiric treatment. Patients should receive beta-lactams for definitive therapy, specifically antistaphylococcal penicillins or cefazolin.
authors.affiliation: Department of Epidemiology, College of Public Health Department of Internal Medicine, Carver College of Medicine, University of Iowa Iowa City Veterans Affairs Health Care System.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: McDanel
authors.affiliation: Department of Epidemiology, College of Public Health Department of Internal Medicine, Carver College of Medicine, University of Iowa Iowa City Veterans Affairs Health Care System.
authors.forename: Eli N
authors.initials: EN
authors.lastname: Perencevich
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa Department of Pathology, Carver College of Medicine, University of Iowa Clinical Quality, Safety, and Performance Improvement, University of Iowa Hospitals and Clinics.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Diekema
authors.affiliation: Department of Epidemiology, College of Public Health Department of Internal Medicine, Carver College of Medicine, University of Iowa Clinical Quality, Safety, and Performance Improvement, University of Iowa Hospitals and Clinics.
authors.forename: Loreen A
authors.initials: LA
authors.lastname: Herwaldt
authors.affiliation: Department of Epidemiology, College of Public Health.
authors.forename: Tara C
authors.initials: TC
authors.lastname: Smith
authors.affiliation: Department of Epidemiology, College of Public Health.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Chrischilles
authors.affiliation: Department of Biostatistics, College of Public Health, University of Iowa, Iowa City.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Dawson
authors.affiliation: Iowa City Veterans Affairs Health Care System.
authors.forename: Lan
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Internal Medicine, Carver College of Medicine, University of Iowa Iowa City Veterans Affairs Health Care System.
authors.forename: Michihiko
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Epidemiology, College of Public Health Department of Internal Medicine, Carver College of Medicine, University of Iowa Iowa City Veterans Affairs Health Care System.
authors.forename: Marin L
authors.initials: ML
authors.lastname: Schweizer
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008875:Middle Aged; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D014640:Vancomycin / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D047090:beta-Lactams / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D014640:Vancomycin
keywords: MSSA; beta-lactams; bloodstream infection; vancomycin