Prediction of treatment success in patients with Enterococcus faecium bacteremia using vancomycin AUC₂₄/MIC ratio: A...

Although vancomycin is commonly used to treat Enterococcus faecium infections, there are no clear guidelines for the optimal 24-h area under the concentration time curve to minimum inhibitory concentration (AUC₂₄/MIC) ratio. This study aimed to determine the target AUC₂₄/MIC ratio associated with vancomycin-treated E. faecium infection outcomes.

This retrospective multicenter cohort study included adult patients who received vancomycin for ≥5 days for E. faecium-associated bloodstream infections between January 2018 and December 2023. The primary outcome was treatment success, defined as a composite of survival beyond 30 days, clinical success, and microbiological eradication. Secondary outcomes included 30-day mortality, clinical success, microbiological eradication, and nephrotoxicity. Receiver operating characteristic (ROC) curve analysis identified the AUC₂₄/MIC cut-off value for treatment success. Multivariate regression analysis was used to determine the association between AUC₂₄/MIC and outcomes.

This study included 81 patients. ROC analysis identified AUC₂₄/MIC ≥427 as the cutoff value for treatment success. The overall treatment success rate (71.6 %) was significantly higher in the above AUC₂₄/MIC cut-off group (81.8 %) than in the below AUC₂₄/MIC cut-off group (59.5 %). On multivariate analysis, AUC₂₄/MIC ≥427 was an independent predictor (adjusted odds ratio: 4.399, 95 % confidence interval: 1.203-19.320, p = 0.024) of treatment success. The clinical success and microbiological eradication rates differed significantly between the below- and above-cut-off groups, whereas nephrotoxicity rates were comparable between the groups.

In treating E. faecium infections, vancomycin AUC₂₄/MIC ratio ≥427 was independently associated with treatment success. However, further prospective studies are required to confirm the AUC₂₄/MIC target.