Is High Vancomycin Minimum Inhibitory Concentration a Good Marker to Predict the Outcome of Methicillin‐ResistantStaphylococcus aureusBacteremia?

To the Editor—A recent article by Peleg et al [1] demonstrated that methicillin-resistant Staphylococcus aureus (MRSA) strains with elevated vancomycin minimum inhibitory concentrations (MICs) were significantly less virulent than strains with lower MICs. From a clinician's perspective, 2 recent articles by Soriano et al [2] and Price et al [3] provided conflicting data regarding mortality risk associated with MRSA bacteremia caused by strains with a high vancomycin MIC (>1 µg/mL). Soriano et al [2] reported an increased mortality associated with MRSA bacteremia, whereas Price et al [3] found just the opposite. We performed a retrospective observational cohort study of patients with MRSA bacteremia from January 2002 through December 2004 in a tertiary-care hospital. Patients were prospectively followed for 3 years. Sixty-three patients with MRSA bacteremia were treated exclusively with vancomycin. Vancomycin MIC was determined by E-test with use of a 0.5 McFarland inoculum in brain-heart infusion agar. The cut off point of vancomycin MIC was 1.5 µg/mL. Thirteen (20.6%) of 63 patients had an MRSA strain with vancomycin MIC ⩾1.5 µg/mL.