title: The impact of vancomycin susceptibility on treatment outcomes among patients with methicillin resistant Staphylococcus aureus bacteremia.
abstract: BACKGROUND
  Management of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia remains a challenge. The emergence of MRSA strains with reduced vancomycin susceptibility complicates treatment.
  
  
  METHODS
  A prospective cohort study (2005-2007) of patients with MRSA bacteremia treated with vancomycin was performed at an academic hospital. Vancomycin minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for stored MRSA isolates. Cox regression analysis was performed to predict 28-day all-cause mortality.
  
  
  RESULTS
  One hundred sixty-three patients with MRSA bacteremia were evaluated. One hundred twelve patients (68.7%) had bacteremia due to MRSA with a vancomycin MIC ≥ 2 ug/mL. Among strains with a vancomycin MIC ≥ 2 ug/mL, 10 isolates (8.9%) were vancomycin-intermediate S. aureus (VISA). Thirty-five patients (21.5%) died within 28 days after the diagnosis of MRSA bacteremia. Higher vancomycin MIC was not associated with mortality in this cohort [adjusted hazard ratio (aHR), 1.57; 95% confidence interval (CI), 0.73-3.37]. Vancomycin tolerance was observed in 4.3% (7/162) of isolates and was not associated with mortality (crude HR, 0.62; 95% CI, 0.08-4.50). Factors independently associated with mortality included higher age (aHR, 1.03; 95% CI 1.00-1.05), cirrhosis (aHR, 3.01; 95% CI, 1.24-7.30), and intensive care unit admission within 48 hours after the diagnosis of bacteremia (aHR, 5.99; 95% CI, 2.86-12.58).
  
  
  CONCLUSIONS
  Among patients with MRSA bacteremia treated with vancomycin, reduced vancomycin susceptibility and vancomycin tolerance were not associated with mortality after adjusting for patient factors. Patient factors including severity of illness and underlying co-morbidities were associated with the mortality.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA. hondah@hotmail.com
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Honda
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Doern
authors.forename: Wm
authors.initials: W
authors.lastname: Michael-Dunne
authors.forename: David K
authors.initials: DK
authors.lastname: Warren
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology; D016470:Bacteremia / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality*; D015331:Cohort Studies; D005260:Female; D006785:Hospitals, University; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality*; D016896:Treatment Outcome; D014640:Vancomycin / Q000008:administration & dosage* / Q000494:pharmacology; D020713:Vancomycin Resistance
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin