4CPS-191 Evaluation of AUC/MIC as a predictor of microbiological and clinical outcomes in staphylococcus gram-positive bacteraemia treated with vancomycin

<h3>Background and Importance</h3> Vancomycin’s role in treating gram-positive infections is well-established. However, the optimal AUC/MIC ratio for non-MRSA Staphylococcal bacteraemia has not been clearly defined. Current guidelines recommend an AUC/MIC ratio of 400–600 mg·h/L for MRSA, but this target may not fully apply to other Staphylococcal species. <h3>Aim and Objectives</h3> To assess whether an AUC/MIC ratio of 400–600 is predictive of clinical and microbiological outcomes in non-MRSA Staphylococcal bacteraemia treated with vancomycin. <h3>Material and Methods</h3> Observational-retrospective study in a tertiary hospital. Adult patients with non-MRSA Staphylococcus bacteraemia treated with vancomycin between January 2020 and June 2024 were registered. Data collected included demographics, AUC/MIC, Bayesian estimated renal clearance, total daily dose, and whether the infection was considered complicated or uncomplicated. Clinical cure was defined as the normalisation of at least two out of three markers (temperature, C-reactive protein, leukocytes) at 72 hours, and microbiological cure as negative blood cultures. Statistical analysis was performed using RStudio (version 2023.12.1), applying logistic regression models to evaluate the relationship between AUC/MIC and both microbiological and clinical outcomes. Receiver operating characteristic (ROC) curves were used to assess the predictive power of the models, and area under the curve (AUC) values were calculated for microbiological and clinical outcomes. <h3>Results</h3> Median age was 63.5 years (SD:14.7), with 58.7% male. Coagulase-negative Staphylococci (CoNS) accounted for 91.3% of cases. The mean Bayesian estimated renal clearance was 5.19 L/h (SD:1.85). The mean total daily dose was 2467.39 mg/day (SD:811.19). The AUC/MIC target of 400–600 was achieved in 37.0% of patients. Additionally, 34.8% had an AUC/MIC below 400, and 28.3% had an AUC/MIC above 600. Of the patients with an AUC/MIC below 400, 12.5% achieved microbiological cure. Overall microbiological cure was 82.6%, with an AUC of 0.845 for the predictive model. Clinical cure was achieved in 50% (AUC=0.773). The inclusion of whether the infection was complicated or uncomplicated did not significantly improve prediction (AUC=0.845). <h3>Conclusion and Relevance</h3> Achieving an AUC/MIC of 400–600 is predictive of microbiological cure, but the predictive ability for clinical cure is lower, likely due to the sample size and limited treatment failures. Further research with larger cohorts is needed to validate these findings, particularly in complicated versus uncomplicated infections. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest