In vitro activity of novel rifamycins against gram-positive clinical isolates.

We describe novel rifamycins that have improved activity, compared with rifampin, against clinical isolates of staphylococci and streptococci, with MIC(90)s of 0.008 and 0.0005 microg/ml, respectively. This enhanced antibacterial activity, along with their potential lack of drug-drug interactions, are considerations that suggest the potential of these novel rifamycins in combination therapy to treat serious Gram-positive infections.