Narasin is a polyether antibiotic produced by the fermentation of Streptomyces aureofaciens, authorized as a coccidiostat feed additive for controlling Eimeria infection, and necrotic enteritis in chickens. The antimicrobial activity of narasin is limited to Gram-positive bacteria including Enterococcus spp., Staphylococcus spp., and Clostridium perfringens.