It is produced by the strain of Str. ostreogriseus NRRL 2558 (NCIB 8792). It has anti-gram positive bacterial activity, and Ostreogrycin A has stronger antibacterial activity than other components. Ostreogrycin A or G has synergistic antibacterial effect with each component of Ostreogrycin B. The Complex has protective effect on mice infected with bacteria by subcutaneous or oral administration.