Vancomycin and Daptomycin Efficacy against MRSA and hVISA: A Study

Strategic Insights -

The emergence of non-susceptible strains of methicillin-resistant Staphylococcus aureus (MRSA), including heterogeneously vancomycin-intermediate S. aureus (hVISA), has led to concerns about the effectiveness of current treatments. Researchers in the United States conducted a study to evaluate the efficacy of vancomycin and daptomycin against vancomycin-susceptible MRSA and hVISA in a pharmacokinetic/pharmacodynamic (PK/PD) model. The study found that daptomycin was more effective against both MRSA and hVISA strains, while vancomycin showed minimal activity against hVISA.

Key Takeaways:

  • The study used six clinical isolates obtained from patients at the Detroit Medical Center: MRSA 494, MRSA 67, hVISA R1720, hVISS R2295, hVISA R3640, and hVISA R1629.
  • Vancomycin regimens of 1 g every 12 h and 2 g every 12 h were tested against MRSA and hVISA isolates, while daptomycin regimens of 6, 10, and 12 mg/kg daily were also tested.
  • Daptomycin was bactericidal against both MRSA and hVISA isolates, achieving rapid and effective kill.
  • Vancomycin showed minimal activity against hVISA, regardless of high dose exposure.
  • The study concluded that daptomycin is a more effective treatment option for MRSA and hVISA infections compared to vancomycin.

Statistics:

  • Six clinical isolates were used in the study: 3 MRSA isolates and 3 hVISA isolates.
  • Daptomycin was tested in 3 different dosing regimens: 6, 10, and 12 mg/kg daily.
  • Vancomycin was tested in 2 different dosing regimens: 1 g every 12 h and 2 g every 12 h.
  • The study was published in the Journal of Antimicrobial Chemotherapy in 2009.
  • The study found that daptomycin achieved 100% kill against both MRSA and hVISA isolates within 24 hours.

Sources:

  • Leonard, S. N. et al. (2009). Evaluation of vancomycin and daptomycin against methicillin-resistant Staphylococcus aureus and heterogeneously vancomycin-intermediate S. aureus in an in vitro pharmacokinetic/pharmacodynamic model with simulated endocardial vegetations. Journal of Antimicrobial Chemotherapy, 63(1), 155-160.
  • Anti-Infectives Week editors (2009). Glycopeptides have historically been the drugs of choice for the treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, the continued selective pressure has led to the emergence of non-susceptible strains including heterogeneously vancomycin-intermediate S. aureus (hVISA).