Relationship between vancomycin exposure and outcomes among patients with MRSA bloodstream infections with vancomycin...

Area of Science:

• Infectious Diseases
• Pharmacokinetics
• Antimicrobial Stewardship

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) pose significant treatment challenges.
• Vancomycin efficacy may be reduced in MRSA infections with elevated vancomycin minimum inhibitory concentrations (MICs).
• Limited data exist on the relationship between vancomycin exposure and outcomes in MRSA BSIs with vancomycin MIC ≥1.5 mg/L.

Purpose of the Study:

• To investigate the association between vancomycin exposure and treatment outcomes in hospitalized adult patients with MRSA BSIs and vancomycin MIC ≥1.5 mg/L.
• To determine if achieving a specific vancomycin exposure threshold (AUC/MIC) is associated with lower treatment failure rates.

Main Methods:

• Retrospective cohort study of 71 adult, non-dialysis patients with MRSA BSIs treated with vancomycin.
• Vancomycin minimum inhibitory concentrations (MICs) were determined using Etest®.
• Area under the concentration-time curve (AUC) was estimated, and achievement of a CART-derived AUC24-48h threshold of 550 mg*h/L (AUC/MIC of 366 mg*h/L) was assessed.

Main Results:

• Most patients (68/71) had a vancomycin MIC_Etest of 1.5 mg/L.
• Achievement of the CART-derived vancomycin AUC_24-48h threshold of 550 mg*h/L was associated with a lower incidence of treatment failure.
• Multivariate analysis indicated a risk ratio of 0.45 for achieving this threshold, suggesting a 2-fold decrease in treatment failure risk.

Conclusions:

• Vancomycin exposure, specifically achieving an AUC_24-48h of at least 550 mg*h/L, may be associated with improved outcomes in patients with MRSA BSIs and vancomycin MIC ≥1.5 mg/L.
• These findings support the potential benefit of optimizing vancomycin dosing in this patient population.
• Further prospective studies are warranted to confirm these results.