title: Antibiotic choice may not explain poorer outcomes in patients with Staphylococcus aureus bacteremia and high vancomycin minimum inhibitory concentrations.
abstract: BACKGROUND
  There are concerns about reduced efficacy of vancomycin in patients with Staphylococcus aureus bacteremia (SAB), especially when the minimum inhibitory concentration (MIC) nears the upper limit of the susceptible range.
  
  
  METHODS
  We examined the relationship between antibiotic treatment, 30-day mortality, and microbiologic parameters in a large Australasian cohort of patients with SAB.
  
  
  RESULTS
  We assessed 532 patients with SAB from 8 hospitals. All patients with methicillin-resistant S. aureus (MRSA) bacteremia were treated with vancomycin, and patients with methicillin-susceptible S. aureus (MSSA) bacteremia received either flucloxacillin or vancomycin. Increasing vancomycin MIC was associated with increased mortality in vancomycin-treated patients. However, even in patients with MSSA bacteremia treated with flucloxacillin, mortality was also higher if the vancomycin Etest MIC of their isolate was >1.5 μg/mL, compared with those with lower MIC isolates (26.8% vs 12.2%; P < .001). After adjustment in a multivariate model, age, hospital-onset SAB and vancomycin MIC were independently associated with mortality, but methicillin resistance and antibiotic choice were not.
  
  
  CONCLUSIONS
  We have confirmed an association between higher vancomycin MIC and increased mortality in patients with SAB, but surprisingly this relationship was not related to the antibiotic treatment received, suggesting that the use of vancomycin per se is not responsible for the poorer outcome.
authors: Department of Infectious Diseases, Austin Health, Heidelberg, Australia. natasha.holmes@austin.org.au
authors: Natasha E
authors: NE
authors: Holmes
authors: John D
authors: JD
authors: Turnidge
authors: Wendy J
authors: WJ
authors: Munckhof
authors: James O
authors: JO
authors: Robinson
authors: Tony M
authors: TM
authors: Korman
authors: Matthew V N
authors: MV
authors: O'Sullivan
authors: Tara L
authors: TL
authors: Anderson
authors: Sally A
authors: SA
authors: Roberts
authors: Wei
authors: W
authors: Gao
authors: Keryn J
authors: KJ
authors: Christiansen
authors: Geoffrey W
authors: GW
authors: Coombs
authors: Paul D R
authors: PD
authors: Johnson
authors: Benjamin P
authors: BP
authors: Howden
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000188:drug therapy* / Q000401:mortality; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015999:Multivariate Analysis; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000401:mortality; D013211:Staphylococcus aureus / Q000187:drug effects*; D016896:Treatment Outcome; D014640:Vancomycin / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin