Tyrothricin

Tyrothricin is an antibiotic peptide complex produced and extracted from the aerobic Gram-positive bacillus Brevibacillus parabrevis which was previously categorized as Bacillus brevis and Bacillus aneurinolyticus . This complex is a mixture comprised of 60% tyrocidine cationic cyclic decapeptides (consisting largely of the six predominant tyrocidines, TrcA/A1, TrcB/B1, TrcC/C1, and other more minor contributors) and 40% neutral linear gramicidins (where valine-gramicidin A is often the major gramicidin present, although the mixture composition can vary) . Moreover, tyrothricin possesses broad spectrum Gram-positive antibacterial and antifungal activity that has not seen many - if any - significant reportings of microbial resistance during the over 60 years of therapeutic use the complex has provided . Nevertheless, as tyrothricin is both cytolytic and hemolytic, it does demonstrate systemic toxicity , although certain formulations that are safe for human use like throat lozenges do exist .