Bacitracin

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Bacitracin is a polypeptide antibiotic produced by the bacteria Bacillus licheniformis. It’s a mixture of related cyclic peptides that mainly targets Gram-positive bacteria and works by disrupting the bacterial cell wall-building process.

What it’s used for
- Topical applications: commonly found in ointments (often with polymyxin B and neomycin in “triple antibiotic” products) to treat or prevent minor skin infections and wounds.
- Eye infections: available as an ophthalmic solution.
- Internal use is avoided because it can damage the kidneys.

How it works
- Bacitracin blocks the dephosphorylation of bactoprenol, a carrier molecule needed to move building blocks for the cell wall to the outside of the bacterial membrane. This stops cell wall synthesis and bacterial growth.

Safety and side effects
- Generally safe when used on the skin, but rare allergic reactions can occur, especially in people who are allergic to neomycin.
- Nephrotoxicity can happen if used internally or in large amounts.

Origin and history
- Bacitracin comes from Bacillus licheniformis and was first discovered in 1945, linked to a strain called Tracey I.
- It was approved by the U.S. FDA in 1948.

Availability and resistance
- Commonly used in topical form, including in Neosporin-type products.
- Also approved for use in animals (e.g., chickens and turkeys), which contributes to concerns about antibiotic resistance when used broadly.
- It is a narrow-spectrum antibiotic, mainly affecting Gram-positive bacteria.