The crucial relationship between vancomycin minimum inhibitory concentration and therapeutic efficacy against methicillin-resistant coagulase-negative staphylococci

The area under the curve (AUC)/minimum inhibitory concentration (MIC) ratio was used as an indicator of the clinical efficacy of vancomycin. However, the target AUC/MIC has not been set for methicillin-resistant coagulase-negative staphylococci (MR-CNS), and the effectiveness of vancomycin in strains with high MIC is unknown. Therefore, we aimed to investigate the relationship between the vancomycin MIC and therapeutic efficacy in patients with MR-CNS bacteremia. The primary outcome was the difference in treatment failure rate when the MR-CNS vancomycin MIC was 1 or 2 µg/mL. The treatment failure rate did not significantly differ between the two groups (MIC 1 vs. MIC 2: 27.0% vs. 31.0%; <i>p</i> = 0.779). As a result of multivariate analysis, AUC/MIC_{0-24 h} ≤230 was extracted as risk factor for treatment failure, suggesting the importance of a sufficient initial loading dose and early blood concentration monitoring to increase AUC/MIC_{0-24 h} for successful treatment.