Erythromycin is produced by a strain of Saccharopolyspora erythraea (formerly Streptomyces erythraeus) and belongs to the macrolide group of antibiotics. It is basic and readily forms salts with acids but it is the base which is microbiologically active. Erythromycin base is (3R *, 4S *, 5S *, 6R *, 7R *, 9R *, 11R *, 12R *, 13S *, 14R *)-4[(2,6-Dideoxy-3-C-methyl3-O-methyl--L-ribo-hexopyranos...