Avilamycin B is a chlorine-containing polysaccharide antibiotic produced by Streptomyces viridochromogenes. The avilamycins, are collectively known as orthosomycins, are active against Gram-positive bacteria and are used for growth promotion and prevention of necrotic enteritis in animals. Avilamycin B contains an acetyl group in place of the isobutyl group of avilamycin A, and is a minor analogue in the commercial product Surmax™.