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.

Methicillin-Resistant Staphylococcus aureus Bacteremia Treated With Vancomycin Calculated by Area-Under-the-Curve in Patients With Elevated Vancomycin Minimum Inhibitory Concentrations

“…1 However, data are divided due to the different MIC testing methods used within these studies. [4][5][6][7][8] There are several automated and manual susceptibility testing methods available for vancomycin, with broth microdilution being the reference standard. Historically, broth microdilution has been used to determine the susceptibilities of pathogenic organisms to multiple antibiotics with high accuracy.…”