Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy. As a polypeptide, toxic, and difficult to use chemical, bacitracin doesn't work well orally, however is very effective topically. Bacitracin exerts pronounced antibacterial action in vitro against a variety of gram-positive and a few gram-negative organisms. However, among systemic diseases, only staphylococcal infections qualify for consideration of bacitracin therapy. Bacitracin is composed of a mixture of related compounds with varying degrees of antibacterial activity. Notable fractions include bacitracin A, A1, B, B1, B2, C, D, E, F, G, and X. Bacitracin A has been found to have the most antibacterial activity. Bacitracin intereferes with the dephosphorylation of the 55-carbon, biphosphate lipid transport molecule C55-isoprenyl pyrophosphate (undecaprenyl pyrophosphate), which carries the building blocks of the peptidoglycan bacterial cell wall outside the inner membrane for construction. Bacitracin binds divalent transition metal ions (Mn(II), Co(II), Ni(II), Cu(II), and Zn(II)) which binds and oxidatively cleave DNA. Used for the treatment of infants with pneumonia and empyema caused by staphylococci shown to be susceptible to the drug. Also used in ointment form for topical treatment of a variety of localized skin and eye infections, as well as for the prevention of wound infections. Used against gram positive bacteria. Bacitracin is also used as an inhibitor of proteases and other enzymes. However, specific activity of bactracin's inhibition of protein disulfide isomerase has been called into question.