29-Nordammara-17(20),24-dien-21-oicacid, 16-(acetyloxy)-3,11-dihydroxy-, (3a,4a,8a,9b,11a,13a,14b,16b,17Z)- (6990-06-3)

Fusidic acid (CAS No.6990-06-3) is a bacteriostatic antibiotic that is often used topically in creams and eyedrops, but may also be given systemically as tablets or injections. The global problem of advancing antimicrobial resistance has led to a renewed interest in its use recently.It is active in vitro against Staphylococcus aureus, most coagulase-negative staphylococci, Corynebacterium species, most clostridium species. Fusidic acid has no useful activity against enterococci or most Gram-negative bacteria (except Neisseria, Moraxella, Legionella pneumophila and Bacteroides fragilis). Fusidic acid is active in vitro and clinically against Mycobacterium leprae but has only marginal activity against Mycobacterium tuberculosis.One important use of fusidic acid clinically is its activity against methicillin-resistant Staphylococcus aureus.Many strains of MRSA remain sensitive to fusidic acid, but because there is a low genetic barrier to resistance (a single point mutation is all that is required), fusidic acid must never be used on its own to treat serious MRSA infection and should be combined with another antimicrobial such as rifampicin.