Activity of novobiocin against methicillin-resistant Staphylococcus aureus

As infections due to methicillin-resistant Staphylococcus aureus become increasingly prevalent, newer alternative antibiotics, especially those which are orally administered, will be required. In order to provide an in-vitro basis for selecting alternative antibiotics, we studied the susceptibility of 103 strains of methicillin-resistant Staph. aureus from seven institutions to oral antimicrobial agents. Novobiocin, rifampicin, and trimethoprim-sulphamethoxazole had excellent in-vitro activity against virtually all strains of methicillin-resistant Staph. aureus. The MIC90 and MBC90 of novobiocin against methicillin-resistant Staph. aureus were 0.25 mg/l. Since previously reported achievable serum levels with oral novobiocin are 100 to 200 times its MIC90 against methicillin-resistant Staph. aureus, novobiocin should be evaluated further for combination therapy with rifampicin or trimethoprim-sulphamethoxazole.