Background: Vancomycin (VAN) remains a primary treatment option for methicillin-resistant Staphylococcus aureus (MRSA) complicated skin and soft tissue infections (cSSTI) though optimal VAN exposure is unknown. The objective of this study was to identify VAN exposure associated with early clinical success and decreased length of hospital stay (LOS).
Methods: Retrospective cohort study conducted in a large academic center in Detroit, MI. Hospitalized patients who received VAN for culture-proven MRSA cSSTI were included. VAN exposure was expressed as the initial 24 hour area under the curve (AUC0-24) to minimum inhibitory concentration (MIC) ratio. VAN AUC0-24 was determined using Bayesian simulation; MIC was determined via broth microdilution (BMD) according to CLSI guidelines. Classification and regression tree (CART) analysis was performed to identify VAN AUC0-24:MIC thresholds associated with early clinical success and LOS < 3 days. Early clinical success was defined as resolution of systemic signs of infection within 72 hours of VAN initiation.
Results: 26 patients were included in the analysis. The most common types of cSSTI included abscess (65.4%), surgical wound (19.2%), and cellulitis (11.5%). Early clinical response was observed in 61.5% of cases. VAN MIC via BMD was 0.5-1 µg/mL in all cases. AUC0-24:MIC > 486 was associated with early clinical response the CART analysis (Figure 1), and remained a significant predictor of early clinical response in the regression model (P = 0.004). No significant associations between AUC0-24:MIC and LOS </= 3 days were observed.
Conclusion: In this cohort of hospitalized patients with MRSA cSSTI, VAN AUC0-24:MIC > 476 was an independent predictor of early clinical response, but not LOS.
Figure 1. VAN AUC0-24:MIC and Early Clinical Response
M. J. Rybak, None