In vitro evaluation of ramoplanin (A16686 or MDL62198). A new depsipeptide complex for potential topical use.

Ramoplanin, a new depsipeptide complex, was found to be 4- to 8-fold more active than vancomycin against all Gram-positive species (500 strains). Similarly, ramoplanin was both more active and had an additional spectrum compared to mupirocin (formerly pseudomonic acid) against Bacillus spp., Corynebacterium jeikeium, enterococci and Listeria monocytogenes. Mupirocin-resistant Staphylococcus spp. strains (less than 1%) were identified in these organisms collected from over 40 medical centers in the United States. These strains (S. capitis and S. saprophyticus) were susceptible to ramoplanin at 0.25 micrograms/ml or less. The three tested antimicrobial agents were not effective against Gram-negative organisms (20 species tested). Ramoplanin was bactericidal and MICs were not adversely influenced by high (greater than or equal to 10(7) CFU/ml) inoculum concentrations. Because ramoplanin has previously shown promise as a topical drug, these in vitro results further substantiate its wide spectrum, potency, and potential clinical usefulness as mupirocin-resistant staphylococci and other Gram-positive species become more prevalent.