Comparative in-vitro activity of vancomycin, teicoplanin, ramoplanin (formerly A16686), paldimycin, DuP 721 and DuP 105 against methicillin and gentamicin resistant Staphylococcus aureus.

The in-vitro activities of five anti-staphylococcal agents, teicoplanin, ramoplanin, paldimycin, DuP 721 and DuP 105 have been compared to vancomycin. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) have been determined for a collection of methicillin and gentamicin resistant Staphylococcus aureus (MGRSA), comprising 75 strains obtained from 22 centres. In terms of geometric mean MICs (inoculum size 10(5) cfu) paldimycin was the most active agent (0.4 mg/l) followed by ramoplanin (0.75 mg/l), teicoplanin (1.0 mg/l), DuP 721 and vancomycin (2.0 mg/l) and DuP 105 (6.8 mg/l). Ramoplanin was bactericidal within six hours to all strains at a concentration of 1.0 mg/l. The MBC90s for vancomycin and teicoplanin were greater than 32 mg/l after 22 h exposure to antibiotic and 2.5 and 4.0 mg/l respectively after 26 h exposure. Paldimycin was bactericidal against only some strains, while DuP 721 and DuP 105 were not bactericidal. Ramoplanin is the most interesting of the new antibiotics, on account of its rapid and consistent bactericidal activity.