ChEBI: Erythromycin A is an erythromycin that consists of erythronolide A having 2,6-dideoxy-3-C-methyl-3-O-methyl-alpha-L-ribo-hexopyranosyl and 3,4,6-trideoxy-3-(dimethylamino)-beta-D-xylo-hexopyranosyl residues attahced at positions 4 and 6 respectively. It is an erythromycin and a cyclic ketone. It derives from an erythronolide A. It is a conjugate base of an erythromycin A(1+).NCI Thesaurus (NCIt): Erythromycin is a broad-spectrum, macrolide antibiotic with antibacterial activity. Erythromycin diffuses through the bacterial cell membrane and reversibly binds to the 50S subunit of the bacterial ribosome. This prevents bacterial protein synthesis. Erythromycin may be bacteriostatic or bactericidal in action, depending on the concentration of the drug at the site of infection and the susceptibility of the organism involved.