Comparison of Vancomycin Treatment Failures for Methicillin-Resistant Staphylococcus aureus Bacteremia Stratified by Minimum Inhibitory Concentration

Abstract

Background: Optimal treatment of methicillin-resistant Staphylococcus aureus bacteremias (MRSABs) with vancomycin minimum inhibitory concentrations (MICs) high within the susceptible range is of concern due to the high rate of mortality and increased prevalence. Objective: The purpose of this study is to evaluate vancomycin treatment failures in patients with MRSAB stratified by vancomycin MIC. Methods: In this retrospective chart review, patients ≥19 years of age with MRSAB between July 2010 and December 2016 were included if they received intravenous vancomycin for ≥72 hours. Vancomycin treatment failures were compared between patients with vancomycin MICs of ≤1 mg/L and 2 mg/L. Vancomycin treatment failure was defined as microbiological failure at 7 days. Inpatient mortality, 30-day readmission, vancomycin-associated nephrotoxicity, and early bacteremia clearance at 48 to 96 hours were assessed as secondary endpoints. Results: Fifty-eight patients were included in the vancomycin MIC ≤1 mg/L group and 22 patients in the vancomycin MIC 2 mg/L group. No significant difference was found in vancomycin treatment failures at 7 days between groups (88% vs 91%, respectively; P = .850). At 96 hours, there was no significant difference in vancomycin treatment failures between groups (72% vs 90%, respectively; P = .127). No significant difference was found in mortality (P > .99) or 30-day readmission (P > .99). Conclusions: In this study, vancomycin treatment failures were not more prevalent in patients with vancomycin MIC of 2 mg/L at 7 days. Regardless of MIC, antibiotics should be switched to an alternative agent at 7 days for persistent bacteremia.