Relationship between vancomycin exposure and outcomes among patients with MRSA bloodstream infections with vancomycin Etest® MIC values of 1.5mg/L: A pilot study.

Data suggest that vancomycin is less effective for methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) with vancomycin Etest® MIC (MIC) ≥1.5 mg/L. No published studies have evaluated the relationship between vancomycin exposure and outcomes among patients with MRSA BSIs vancomycin MIC ≥1.5 mg/L. This study was a retrospective cohort of 71 hospitalized, adult, non-dialysis patients with MRSA BSIs treated with vancomycin. All but three patients had a vancomycin MIC of 1.5 mg/L. Achievement of CART-derived AUC of at least 550 mgh/L (AUC/MIC of 366 mgh/L) was associated with a lower incidence of treatment failure. In multivariate analyses, the risk ratio was 0.45 for the CART-derived AUC threshold, indicating that achievement of the CART-derived AUC threshold of 550 was associated with a 2-fold decrease in treatment failure. These findings suggest a potential association between vancomycin exposure and outcomes in patients with MRSA BSIs with MIC ≥1.5 mg/L. As this study was retrospective, these findings provide the basis for a future large-scale, multi-center prospective study.