Ramoplanin versus methicillin-resistant Staphylococcus aureus: in vitro experience.
The authors have investigated the activity of ramoplanin against 162 isolates of MRSA from some twenty-six countries around the world. MICs were determined by the plate dilution method in isosensitest agar with an inoculum of 10(6) cfu. MBCs were measured by replication, using velvet pads, from MIC plates after 24 h incubation at 37 degrees C. Time-kill curves were determined from viable counts of cultures in Isosensitest broth (inoculum ca. 5.0 x 10(6) cfu/ml) taken at intervals during shaking culture at 37 degrees C for up to 24 h. Ciprofloxacin, mupirocin, rifampicin, teicoplanin and vancomycin were used as comparison compounds. The following MIC90 (MBC90) values (mg/l) were obtained against a selection of 60 strains: ciprofloxacin 0.8 (1.8), mupirocin 0.27 (19.0), ramoplanin 0.5 (1.0), rifampicin 0.007 (0.01), teicoplanin 1.2 (greater than 32) and vancomycin 2.2 (greater than 32.0). In time-kill experiments, ramoplanin at 20 mg/l and ciprofloxacin at 3.0 mg/l produced 99.9% killing in less than 4h. Mupirocin at 4.0 mg/l was only slowly bactericidal. No resistance was found to mupirocin, ramoplanin, teicoplanin or vancomycin in the 162 isolates tested, whereas ca. 20% resistance was found to ciprofloxacin and rifampicin. The absence of resistance, the high intrinsic activity and the rapid bactericidal effect of ramoplanin against this diverse group of MRSA are very encouraging, and suggest that clinical trials are indicated.
Brumfitt
W
W
Department of Medical Microbiology, Royal Free Hospital, Hampstead, London, UK.
Maple
P A
PA
Hamilton-Miller
J M
JM
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D047630:Depsipeptides; D004352:Drug Resistance, Microbial; D006020:Glycopeptides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests / Q000379:methods; D010456:Peptides, Cyclic; D013211:Staphylococcus aureus / Q000187:drug effects*
D000900:Anti-Bacterial Agents; D047630:Depsipeptides; D006020:Glycopeptides; D010456:Peptides, Cyclic; C041438:ramoplanin