Midecamycin, an acetoxy-substituted macrolide antibiotic, is tested against gram-positive and gram-negative bacteria. IC50 & Target: Antibacterial^[1] In Vitro: Midecamycin inhibits the majority of streptococci, staphylococci, and strains of Haemophilus and Listeria at concentrations of less than 3.1 μg/mL^[1]. Midecamycin is a 16-membered macrolide. Midecamycin is a new macrolide antibiotic, which is produced by Streptomyces mycarofaciens^[2].