title: Empiric antibiotic therapy for Staphylococcus aureus bacteremia may not reduce in-hospital mortality: a retrospective cohort study.
abstract: BACKGROUND
  Appropriate empiric therapy, antibiotic therapy with in vitro activity to the infecting organism given prior to confirmed culture results, may improve Staphylococcus aureus outcomes. We aimed to measure the clinical impact of appropriate empiric antibiotic therapy on mortality, while statistically adjusting for comorbidities, severity of illness and presence of virulence factors in the infecting strain.
  
  
  METHODS
  We conducted a retrospective cohort study of adult patients admitted to a tertiary-care facility from January 1, 2003 to June 30, 2007, who had S. aureus bacteremia. Time to appropriate therapy was measured from blood culture collection to the receipt of antibiotics with in vitro activity to the infecting organism. Cox proportional hazard models were used to measure the association between receipt of appropriate empiric therapy and in-hospital mortality, statistically adjusting for patient and pathogen characteristics.
  
  
  RESULTS
  Among 814 admissions, 537 (66%) received appropriate empiric therapy. Those who received appropriate empiric therapy had a higher hazard of 30-day in-hospital mortality (Hazard Ratio (HR): 1.52; 95% confidence interval (CI): 0.99, 2.34). A longer time to appropriate therapy was protective against mortality (HR: 0.79; 95% CI: 0.60, 1.03) except among the healthiest quartile of patients (HR: 1.44; 95% CI: 0.66, 3.15).
  
  
  CONCLUSIONS
  Appropriate empiric therapy was not associated with decreased mortality in patients with S. aureus bacteremia except in the least ill patients. Initial broad antibiotic selection may not be widely beneficial.
authors.affiliation: Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States of America. marin-schweizer@uiowa.edu
authors.forename: Marin L
authors.initials: ML
authors.lastname: Schweizer
authors.forename: Jon P
authors.initials: JP
authors.lastname: Furuno
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Harris
authors.forename: J Kristie
authors.initials: JK
authors.lastname: Johnson
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Shardell
authors.forename: Jessina C
authors.initials: JC
authors.lastname: McGregor
authors.forename: Kerri A
authors.initials: KA
authors.lastname: Thom
authors.forename: George
authors.initials: G
authors.lastname: Sakoulas
authors.forename: Eli N
authors.initials: EN
authors.lastname: Perencevich
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology* / Q000401:mortality; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000401:mortality*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents