TYROTHRICIN

At the Rockefeller Institute in New York in 1939, Rene Dubos isolated a bactericidal, proteinfree extract from Bacillus brevis.11 This material, tyrothricin, was soon shown to consist mainly of a cyclic decapeptide called tyrocidin, together with a similar compound called gramicidin S, which was 50 times as potent.12 Their structures were elucidated by Richard Synge at the Lister Institute in London using paper chromatography in one of its earliest applications.13,14 Although both components were able to protect mice against pneumococci, they were too toxic for general use.
 
Tyrothricin was suitable only for topical application. It was marketed in the USA by Sharp & Dohme in 1942 for treatment of Gram-positive infections. Since then, it has been universally used in throat lozenges as a non-prescription antibiotic, but the commercial success of this type of product has been largely due to the incorporation of benzocaine, a topical anaesthetic that soothes sore throats.

White or almost white powder.

Tyrothricin is a complex of two unrelated peptide families, gramicidin complex and tyrocidines complex, produced by Bacillus brevis and discovered by Dubos in 1939. Typically, tyrothricin is composed of 20% of the linear pentadecylpeptide gramicidins and 80% of cyclic decapeptide tyrocidines. Both the gramicidins and tyrocidines act by disrupting bacterial cell wall integrity, but by differing mechanisms. Tyrothricin is used clinically for bacterial skin infections in some countries.

An antibiotic produced by growth of Bacillus brevis. It consists of a mixture of antibiotics, principally gramicidin and tyrocidine. Gramicidin is the more active component. Use is generally limited to local external applications. It is active against some Gram-positive bacteria, including species of pneumococci, streptococci, and staphylococci.

Bactratycin (Wallace).