Retrospective observational study comparing vancomycin versus daptomycin as initial therapy for Staphylococcus aureus...

Area of Science:

• Infectious Diseases
• Pharmacology
• Clinical Medicine

Background:

• Limited data exist comparing vancomycin alternatives for Staphylococcus aureus infections with vancomycin Minimum Inhibitory Concentration (MIC) >1.
• The study addresses the need for comparative data on daptomycin versus vancomycin in treating S. aureus infections, particularly in settings with elevated vancomycin MICs.

Purpose of the Study:

• To evaluate and compare outcomes of S. aureus infections treated with initial daptomycin versus vancomycin therapy.
• To assess treatment efficacy in a patient population where most S. aureus isolates exhibited vancomycin MICs of 2 mg/L.

Main Methods:

• Retrospective chart review at a 450-bed acute care hospital.
• Inclusion criteria: patients >18 years receiving initial vancomycin or daptomycin for ≥3 days for S. aureus infection (Nov 2006-Jul 2008).
• Exclusion criteria: endocarditis, osteomyelitis, CNS infections, or S. aureus respiratory tract infections.

Main Results:

• 165 patients included: 57 (35%) received daptomycin, 108 (65%) received vancomycin. 78% had vancomycin MICs of 2 mg/L.
• Daptomycin group had a significantly shorter median antibiotic-related length of stay (7.5 vs 10.0 days; P=0.035).
• Thirty-day all-cause mortality did not differ significantly (7% daptomycin vs 6% vancomycin; P=0.708). Relapse rates were comparable in the overall population but favored daptomycin in S. aureus bacteremia with MIC 2 mg/L (0% vs 26%; P=0.089).

Conclusions:

• In settings with prevalent S. aureus infections having vancomycin MICs of 2 mg/L, daptomycin was associated with a significantly shorter antibiotic-related length of stay compared to vancomycin.
• Prospective studies are recommended to confirm daptomycin's benefits over vancomycin in specific infections, especially those with unfavorable vancomycin MICs.