Tyrothricin is an antibiotic that belongs to the group of polypeptide antibiotics (actinomycin, bacitracin, polymyxins). Tyrothricin is a mixture of various antibacterially active polypeptides from the groups of tyrocidins (70-80%) and gramicidins (20-30%). The substances are formed by the anaerobic, spore-forming Bacillus brevis. Their range of action primarily covers gram-positive bacteria (including methicillin-resistant Staphylococcus aureus strains - MRSA); some gram-negative bacteria and various types of fungi (e.g. Candida albicans) are also covered.
Tyrothricin is classified as a polypeptide antibiotic, which also includes actinomycin, bacitracin and the polymyxins.
Tyrocidin causes the release of essential nitrogen and phosphatide-containing substances in the bacterial cell by destroying the osmotic barrier of the cell membrane. Gramicidin causes the formation of additional cation-conducting channels, resulting in a loss of potassium from the bacterial cell. The direct attack on the cell membrane is one of the reasons why resistance does not occur when tyrothricin is used.
Tyrothricin has no effect on the body's own tissue and therefore does not interfere with the cellular processes involved in wound healing (unlike many antiseptics, which have a cytotoxic effect).