Vancomycin-Resistant Enterococcal Bacteremia in a Hematology Unit: Risk Factors for Mortality and Impact of Adequate Antimicrobial Therapy on Mortality

ABSTRACT

BACKGROUND: Vancomycin resistant enterococcal (VRE) bacteremia is increasing among patients with hematologic malignancies. Our study was to determine the clinical characteristics, risk factors for mortality, and effect of adequate antimicrobial therapy on outcome in patients with hematologic malignancies who developed VRE bacteremia. MATERIALS AND METHODS: we retrospectively reviewed episodes of VRE bacteremia in 90 patients with hematologic malignancices from January 1997 to December 2006. Adequate antimicrobial therapy was defined as the use of linezolid or quinupristin/dalfopristin, initiated within 72 hours of initial positive blood culture and continuing for at least 48 hours. Outcome was evaluated at 14 and 28 days after onset of bacteremia. RESULTS: The overall 14-day and 28-day mortality rates were 44.4% (40/90) and 54.4% (49/90) respectively. Failure of neutrophil recovery (odds ratio [OR], 40.29; 95% confidence interval [CI], 6.22 to 260.72; P< or =0.001) and increased APACHE II score (OR, 1.30; 95% CI, 1.07 to 1.58; P=0.008) were independent risk factors for 14-day as well as for 28-day mortality. To specifically examine the effects of adequate antimicrobial therapy, we performed a separate analysis of the 14-day mortality, after excluding 6 patients who died within 48 hours of bacteremia onset. Multivariate analysis showed that failure of neutrophil recovery (OR, 42.10; 95% CI, 5.77 to 307.00; P< or =0.001) and increased APACHE II score (OR, 1.25; 95% CI, 1.02 to 1.53; P=0.026) were still independently associated with mortality. Adequate antimicrobial therapy, however, did not have a protective effect (OR, 1.91; 95% CI, 0.50 to 7,22; P= 0.338). Of the 65 patients with monomicrobial bacteremia, 30 (46.2%) received adequate antimicrobial therapy and 35 (53.8%) did not their 14-day mortality rates were 40.0% (12/30) and 42.9% (15/35), respectively (P=0.816). CONCLUSION: In conclusion, severity of underlying illness was associated with mortality. Adequacy of antimicrobial therapy did not improve survival, this may be due to low virulence of enterococci and severity of underlying disease.