In vitro activity of RU 64004, a new ketolide antibiotic, against gram-positive bacteria

The comparative in vitro activity of RU 64004 (also known as HMR 3004), a new ketolide antibiotic, was tested qv agar dilution against approximately 500 gram-positive organisms, including multiply resistant enterococci, streptococci, and staphylococci. All streptococci were inhibited by less than or equal to 1 mu g of RU 64004 per ml, The ketofide was more potent than other macrolides against erythromycin A-susceptible staphylococci and was generally more potent than clindamycin against erythromycin A-resistant strains susceptible to this agent, Clindamycin-resistant staphylococci (MIC, >128 mu g/ml) proved resistant to the ketolide, but some erythromycin A- and clindamycin-resistant enterococci remained susceptible to RU 64004.