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Spiramycin is a macrolide antibiotic produced by Streptomyces ambofaciens. It is active against the following Gram-positive organisms: Staphylococcus aureus (including penicillin resistant strains), ß-haemolytic streptococci, Streptococcus viridans, Streptococcus faecalis and Streptococcus pneumoniae, Corynebacterium diphteriae, clostridia. Except for Bordetella pertussis, Hemophilus influenzae (approximately 50% of strains) and neisseria, gram-negative organisms are generally considered as resistant to spiramycin. Bacterial resistance to spiramycin has been reported to develop, including cross-resistance between spiramycin and erythromycin. However, most of the erythromycin-resistant strains of S. aureus are still sensitive to spiramycin.
Pharmacology
The mechanism of action of macrolides has been a matter of controversy for some time. Spiramycin, a 16-membered macrolide, inhibits translocation by binding to bacterial 50S ribosomal subunits with an apparent 1 : 1 stoichiometry. This antibiotic is a potent inhibitor of the binding to the ribosome of both donor and acceptor substrates. The primary mechanism of action is done by stimulation of dissociation of peptidyl-tRNA from ribosomes during translocation.