Acetylspiramycin (Spiramycin B; Spiramycin II; Foromacidin B) is a potent and orally active macrolide antibiotic produced by various Streptomyces species, an acetylated derivative of Spiramycin (HY-100593). Acetylspiramycin is an antimicrobial agent with activity against gram-positive organisms, including Streptococcus pyogenes, S. viridans, Corynebacterium diphtheriae and methicillin-sensitive Staphylococcus aureus. Acetylspiramycin is also a potent antiprotozoal agent that against parasitic Infectii caused by Cryptosporidium spp.