Relationship of in vitro synergy and treatment outcome with daptomycin plus rifampin in patients with invasive methicillin-resistant Staphylococcus aureus infections.

ABSTRACT

We report the findings of a study examining the relationship between in vitro daptomycin-rifampin synergy and the therapeutic outcome of 12 patients with complex deep methicillin-resistant Staphylococcus aureus (MRSA) infections treated for prolonged periods with this combination. Checkerboard synergy was found in nine cases and was 100% predictive of therapeutic success; absence of synergy was found in three cases, two of which were therapeutic failures (P = 0.045). No relationship was observed between synergy and outcome by time-kill assessment. Checkerboard synergy may predict clinical response to daptomycin plus rifampin for complex invasive MRSA infections requiring prolonged treatment.