Bacitracin

Baciim (topical generics)

Bacitracin is a cyclic peptide antibiotic first isolated in the 1940s from Bacillus subtilis/licheniformis (the name comes from a patient named Tracy plus 'bacillus'). It works at a distinctive point in cell-wall construction: bacteria use a lipid carrier (bactoprenol, or C55 undecaprenyl phosphate) to ferry cell-wall building blocks across the membrane, and after each delivery the carrier must be recycled by removing a phosphate group. Bacitracin binds the pyrophosphate form of this lipid carrier and prevents its recycling, so the assembly line for peptidoglycan stalls and the Gram-positive bacterium cannot maintain its cell wall. In practice, bacitracin is overwhelmingly a topical antibiotic. It is a familiar ingredient in over-the-counter first-aid ointments (often combined with neomycin and polymyxin B in 'triple antibiotic' products) used to prevent infection in minor cuts, scrapes, and burns, and it appears in some ophthalmic preparations. Its spectrum is mainly Gram-positive. Bacitracin is largely avoided for systemic (injected) use because it can cause significant kidney toxicity, so its therapeutic role today is essentially topical, where absorption is minimal. A relevant modern caution is that topical bacitracin can occasionally cause allergic contact dermatitis and, rarely, allergic reactions, so persistent rash at an application site warrants attention. Bacitracin is an approved medicine — available over the counter in topical form in many countries — but, like all antibiotics, it should be used appropriately and not applied to large wounds or used long-term without medical advice.