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Daptomycin versus Vancomycin for Bloodstream Infections Due to Methicillin-Resistant Staphylococcus Aureus with A High Vancomycin Minimum Inhibitory Concentration: A Case-Control Study
Moore CL, Osaki-Kiyan P, Haque NZ, et al. Clin Infect Dis. 2012;54(1):51-8.
Study Question: Compared to vancomycin, is daptomycin effective in treating patients with BSI due to methicillin-resistant Staphylococcus aureus (MRSA) isolates with high vancomycin mean inhibitory concentrations (MICs)?
Study Description: This was a single center, retrospective case-control study evaluating clinical treatment success in 177 patients (59 in the daptomycin group; 118 in the control) with a MRSA BSI. Patients included in analysis: received either vancomycin in the control group or daptomycin; had a MRSA isolate from the bloodstream with an MIC of > 1 and < 2 mcg/mL; and were matched by age, APACHE-II score, and source of BSI.
Results: Composite clinical failure was not statistically different between daptomycin and vancomycin-treated patients (17% and 31%, respectively; p = 0.084). Sixty day mortality was statistically lower in daptomycin-treated patients, while microbiologic failure and recurrence were similar between groups. Of patients treated with vancomycin, 21% developed renal insufficiency. One daptomycin-treated patient experienced an elevated CPK which normalized upon discontinuation.
Conclusion(s): There was a significant decrease in 60-day mortality for daptomycin-treated patients, however no difference in clinical failure rates, microbiologic failure, or recurrence of BSI.
Perspective: Of the daptomycin group, 98% of patients were switched from a different initial antibiotic and 91% of these were on vancomycin originally. Patients were changed due to worsening or no improvement in clinical condition, and more patients in the daptomycin group had a vancomycin MIC of 2 mcg/mL. Interestingly, there was no difference in clinical failure for patients with definitive vancomycin levels < 15 mcg/mL compared to ≥ 15 mcg/mL. Worth noting and meriting further research given this study’s observational design is the mortality difference favoring daptomycin in spite of a lack of difference between groups in the primary endpoint.