Effect of Daptomycin Dose on the Outcome of Vancomycin-Resistant, Daptomycin-Susceptible Enterococcus faecium Bacteremia

Background: Treatment options for vancomycin-resistant enterococci (VRE) bloodstream infection (BSI) are limited. Daptomycin, although not currently approved for this indication, is frequently used for the treatment of VRE-BSI. Its optimal dose still needs to be determined. Methods: We conducted a prospective, observational, cohort study during 2010-2015. We included patients who received a daptomycin dose of ≥6 mg/kg for the treatment of VRE-BSI caused by daptomycin-susceptible VRE. The primary endpoint was 14-day mortality, and multivariable logistic regression was performed for outcome analysis. Results: We included 112 patients treated with daptomycin for VRE-BSI and with evaluable clinical outcomes. The daptomycin minimum inhibitory concentration (MIC) was 4 mg/L in 78 (69.6%) and ≤2 mg/L in 34 (30.4%) isolates. The overall mortality was 40/112 (35.7%). The unadjusted mortality was 18/36 (50.0%) for a daptomycin dose of <7 mg/kg, 17/51 (33.3%) for a dose of 7-9 mg/kg, and 5/25 (20%) for a dose of ≥9 mg/kg (P = .05). The best outcomes were associated with a daptomycin dose of ≥9 mg/kg compared to doses of <7 mg/kg (adjusted odds ratio aOR, 10.57; 95% confidence interval CI, 2.25-49.62; P=.003) and 7-9 mg/kg (aOR, 5.01; 95% CI, 1.14-21.98; P=.03). There was no significant difference in mortality with respect to the daptomycin MIC. There was no association between daptomycin dose and elevated creatinine kinase. Conclusion: Higher daptomycin doses (≥9 mg/kg) were associated with lower mortality in patients with VRE-BSI. Our results suggest that higher daptomycin doses need to be considered for VRE-BSI treatment.