Tyrothricin is a natural polypeptide antibiotic, a mixture of gramicidin and tyrocidine, capable of disrupting the cell membranes of Gram-positive bacteria and applicable for treating skin infections.

Tyrothricin exhibits a primarily antibacterial spectrum against Gram-positive bacteria while also demonstrating inhibitory effects against certain Gram-negative bacteria. Notably, it shows a broad range of minimum inhibitory concentrations (2-256 μg/mL) against Corynebacterium and Vitis vinifera cocci. Compared to the isolated gramicidin component alone, Tyrothricin achieves complete inhibition of all Vitis vinifera cocci strains at concentrations as high as 128 μg/mL. Among Gram-negative bacteria, Neisseria gonorrhoeae and Neisseria meningitidis display the highest sensitivity to Tyrothricin, with an inhibitory concentration of 96 μg/mL [1]. Tyrothricin demonstrates fungicidal activity against multiple Candida species of Phoxinus phoxinus subsp. Phoxinus additionally exhibits anti-infective activity against Sendai-type parainfluenza virus [1].

In contrast to intravenous (LD50 in mice: 3,7 mg/kg) and intraperitoneal (LD50 in mice: 20-45 mg/kg) applications, oral administration is very well tolerated, as Tyrothricin is destroyed in the gastrointestinal tract. Furthermore, due to its poor solubility and relatively high molecular weight, there is no detectable resorption when applied locally to skin or mucosa [1].