Early Use of Daptomycin Versus Vancomycin for Methicillin-Resistant Staphylococcus aureus Bacteremia With Vancomycin Minimum Inhibitory Concentration >1 mg/L: A Matched Cohort Study

Abstract

BACKGROUND: Recent reports have described decreased effectiveness with vancomycin treatment for methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) when the vancomycin minimum inhibitory concentration (MIC) is >1 µg/mL. METHODS: This matched, retrospective cohort study compared the clinical effectiveness of daptomycin with that of vancomycin for the treatment of MRSAB with vancomycin MICs >1 µg/mL. The primary outcome was clinical failure, defined as a composite of 30-day mortality or bacteremia persisting for ≥7 days. RESULTS: One hundred seventy patients were matched 1:1 with respect to the antimicrobial administered. In the daptomycin group, all patients received <72 hours of vancomycin (median, 1.7 days [interquartile range, 1.1-2.3 days]) prior to switching to daptomycin. The rate of clinical failure at 30 days was significantly lower in the daptomycin arm compared to the vancomycin arm (20.0% vs 48.2%; P < 0.001). Both 30-day mortality and persistent bacteremia were significantly lower in the daptomycin group compared to the vancomycin group (3.5% vs 12.9% [P = .047] and 18.8% vs 42.4% [P = .001], respectively). Logistic regression confirmed the association between vancomycin treatment and increased risk of clinical failure (adjusted odds ratio, 4.5; 95% confidence interval, 2.1-9.8). CONCLUSIONS: This is the first matched study comparing early daptomycin versus vancomycin for the treatment of MRSAB when the vancomycin MIC is >1 µg/mL. Treatment with daptomycin resulted in significantly improved outcomes, including decreased 30-day mortality and persistent bacteremia. These results support the practice of switching early from vancomycin to daptomycin for the treatment of MRSAB when the vancomycin MIC is >1 µg/mL.