Fusidic Acid

Since its initial isolation from the fungus Fusidium coccineum in 1962, fusidic acid has functioned predominantly as an anti-staphylococcal agent, effective against both Methicillin sensitive and Methicillin resistant staphylococcus aureus infection (MSSA and MRSA). Clinical use has included treatment of skin and soft tissue infections, bone and joint infection as well as less common applications including for endocarditis, respiratory infections in patients with Cystic Fibrosis and staphylococcal bacteremia. A steroidal antibiotic, that retains no steroidal activity, it currently remains the only member of the fusidane antibiotic class available on the market. A unique antibiotic, it also employs a novel method of action by preventing elongation factor G (EF-G) release from the ribosome thus inhibiting bacterial protein synthesis. Resistance rates still remain low, however they have increased over the preceding decade, mainly due to use of monotherapy to treat superficial skin infections. Resistance mechanisms include alterations to the gene encoding EF-G ( fusA ) or to protective proteins of EF-G ( fusB, C, D, and F ). To try and prevent selection of these resistant mutants fusidic acid is primarily used in combination therapy, commonly with rifampicin.