Activity of coumermycin against clinical isolates of staphylococci.

Staphylococci, particularly methicillin-resistant strains of Staphylococcus aureus, are major nosocomial pathogens in large hospitals in eastern Australia. At present vancomycin is the drug of choice for the treatment of life-threatening methicillin-resistant S. aureus infections. A possible alternative drug is coumermycin, a bis-hydroxy coumarin which inhibits DNA gyrase. Coumermycin activity was determined against clinical isolates from the Royal Melbourne Hospital. MICs of 639 staphylococcal isolates were determined by agar dilution. MICs and MBCs of 100 staphylococcal isolates were also determined by microdilution methods. The results showed that coumermycin was bactericidal, with MBCs of less than or equal to 4 micrograms/ml against all isolates tested. The results indicate that coumermycin is a potential alternative to vancomycin in the treatment of severe staphylococcal infections.