Virginiamycin B is a depsipeptide antibiotic co-produced with ostreogrycin A, together used as a synergistic mixture. Virginiamycin B, also known as ostreogrycin B and streptogramin B among other synonyms, was discovered independently and named by several groups, leading to considerable confusion in the literature. Virginiamycin B acts a synergist, binding to the conformational change of the peptidyl transferase centre of the 50S ribosome induced by ostreogrycin A.