Virginiamycin is a streptogramin antibiotic similar to pristinamycin and quinupristin/dalfopristin. It is a combination of pristinamycin IIA (virginiamycin M1) and virginiamycin S1.[1] Virginiamycin is used in the fuel ethanol industry to prevent microbial contamination.[2] It is also used in agriculture, specifically in livestock, to accelerate the growth of the animals and to prevent and treat infections. [3] Antibiotics also save as much as 30% in feed costs among young swine, although the savings fade as pigs get older, according to a USDA study.[3]