Treatment success prediction in patients with methicillin-resistant coagulase-negative staphylococci infections, using vancomycin AUC₂₄/MIC ratio: a multicentre retrospective cohort study

Background: Although vancomycin is commonly used to treat methicillin-resistant coagulase-negative staphylococci (MRCoNS) infections, there are no clear guidelines for the optimal 24 h AUC₂₄/MIC ratio. This study aimed to determine the target AUC₂₄/MIC ratio associated with vancomycin-treated MRCoNS infection outcomes. Methods: This multicentre retrospective cohort study included adult patients who received vancomycin for ≥5 days for bloodstream infections caused by MRCoNS between January 2018 and December 2023. 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 was used to identify the AUC₂₄/MIC cut-off for treatment success. Multivariate regression analysis was used to determine the association between AUC₂₄/MIC and outcomes. Results: This study included 147 patients. ROC analysis identified a target AUC₂₄/MIC ≥373 for treatment success. The overall treatment success rate (70.1%) was significantly higher in the above-average AUC₂₄/MIC cutoff group (83.1%) than that in the below AUC₂₄/MIC cut-off group (57.9%). Multivariate analysis confirmed that AUC₂₄/MIC ≥373 was an independent predictor (adjusted OR = 10.227; 95% CI = 3.585–29.171). The 30-day mortality and microbiological eradication rates differed significantly between the below- and above-cut-off groups, whereas nephrotoxicity rates were comparable among the groups. Conclusions: In treating MRCoNS infections, vancomycin AUC₂₄/MIC ratio ≥373 was independently associated with favourable treatment outcomes. However, further prospective studies are required to confirm this target owing to the retrospective nature of this study.