The bacitracins are a mixed group of polypeptide antibiotics. The major constituent is bacitracin A. Bacitracin inhibits cell wall synthesis. A variety of gram-positive cocci and bacilli, Neisseria, H. influenzae, and Treponema pallidum are sensitive to the drug. A unit of the antibiotic is equivalent to 26 ^g of the USP standard.
Bacitracin is available in ophthalmic and dermatologic ointments; the antibiotic also is available as a powder for the preparation of topical solutions. The ointments are applied directly to the involved surface one or more times daily. A number of topical preparations of bacitracin, to which neomycin or polymyxin or both have been added, are available, and some contain the three antibi-oticsplus hydrocortisone. For open infections such as infected eczema and infected dermal ulcers, the local application of the antibiotic may be of some help in eradicating sensitive bacteria. Bac-itracin rarely produces hypersensitivity. Suppurative conjunctivitis and infected corneal ulcer respond well to the topical use of bacitracin when caused by susceptible bacteria. Bacitracin has been used with limited success for eradication of nasal carriage of staphylococci. Oral bacitracin has been used with some success for the treatment of antibiotic-associated diarrhea caused by C. difficile. Serious nephrotoxicity results from the parenteral use of bacitracin. Hypersensitivity reactions rarely result from topical application.
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