Outcomes with daptomycin in the treatment of Staphylococcus aureus infections with a range of vancomycin MICs

OBJECTIVES Recent recommendations by the Infectious Diseases Society of America for the treatment of Staphylococcus aureus suggest the use of alternative agents when vancomycin MIC values are >or=2 mg/L. This study examines the outcome of patients treated with daptomycin for S. aureus infections with documented vancomycin MICs. PATIENTS AND METHODS All patients with skin, bacteraemia and endocarditis infections due to S. aureus with vancomycin MIC values in CORE 2005-08, a retrospective, multicentre, observational registry, were studied. The outcome (cure, improved, failure or non-evaluable) was the investigator assessment at the end of daptomycin therapy. Success was defined as cure or improved. RESULTS Five hundred and forty-seven clinically evaluable patients were identified with discrete vancomycin MIC values [MIC <2 mg/L: 451 (82%); MIC >or=2 mg/L: 96 (18%)]. The vancomycin MIC groups were well matched for patient characteristics, types of infections, first-line daptomycin use (19%) and prior vancomycin use (58%). Clinical success was reported in 94% of patients. No differences were detected in the daptomycin success rate by the vancomycin MIC group overall or by the infection type. A multivariate logistic regression also failed to identify vancomycin MIC as a predictor of daptomycin failure. Adverse event (AE) rates were not different when analysed by MIC group; both groups had approximately 17% of patients with one AE. CONCLUSIONS In this diverse population, daptomycin was associated with similar outcomes for patients, regardless of whether the vancomycin MIC was categorized as <2 or >or=2 mg/L. Further studies are warranted.