It is produced by the strain of Str. kitasatoensis. It's a macrolide antibiotic. It has strong anti-gram-positive bacterial effect, and also has an effect on spirochetes, rickettsium and Chlamydia. After the C3 position on the lactone ring in the structure is acetylated, the activity in vitro is reduced, but the activity in vivo is enhanced, and the toxicity is also reduced. The antibacterial activity of Leucomycin group A is stronger than group B. It has been used in clinical and the indications are the same as erythromycin.