Pristinamycin

Pristinamycin (INN), also spelled pristinamycine, is an antibiotic used primarily in the treatment of staphylococcal infections, and to a lesser extent streptococcal infections. It is a streptogramin group antibiotic, similar to virginiamycin, derived from the bacterium Streptomyces pristina spiralis. It is marketed in Europe by Sanofi-Aventis under the trade name Pyostacine.

Pristinamycin is a mixture of two components that have a synergistic antibacterial action. Pristinamycin I is a macrolide, and results in pristinamycin having a similar spectrum of action to erythromycin. Pristinamycin II is a depsipeptide.

Clinical use
Despite the macrolide component, it is effective against erythromycin-resistant staphylococci and strepcococci. Importantly, it is active against methicillin-resistant Staphylococcus aureus (MRSA). Its usefulness for severe infections, however, may be limited by the lack of an intravenous formulation owing to its poor solubility. Nevertheless it is sometimes used as an alternative to rifampicin+fusidic acid or linezolid for the treatment of MRSA.

The lack of an intravenous formulation led to the development of the pristinamycin-derivative quinupristin/dalfopristin, which may be administered intravenously for more severe MRSA infections.