Mikamycin A, Pristinamycin IIA, Stephylomycin M1, Streptogramin A, Syncothrecin A, Synergistin A1, Virginiamycin M1, Vernamycin A, Antibiotic 14752-2, Antibiotic E129A, Antibiotic PA 114A, Antibiotic 1745Z3A, Antibiotic 547C, Factor M

Ostreogrycin A also commonly referred to as virginiamycin M1 or streptogramin A is the major component of the "virginamycin complex". In the 1950s this complex was independently discovered so many times the literature became highly confusing. Ostreogrycin A is a macrocyclic lactone antibiotic that acts syngeristically with the structurally unrelated cyclic depsipeptides more commonly known as the virginiamycins B (ostreogrycin B or streptogramin B) and S to inhibit peptide elongation. This is achieved by blocking formation of a peptide bond between the growing peptide chain (peptidyl-tRNA) linked to the 50S ribosome and aminoacyl-tRNA. Ostreogrycin A has proven to be highly active against Gram positive bacteria, particularly methicillin-resistant S. aureus.