Bacitracin

Bacitracin is a real cyclic peptide antibiotic, discovered from an infected childhood wound in 1945, now sold almost exclusively as a topical over-the-counter ointment because systemic use turned out to be significantly toxic to the kidneys.

A real discovery story

Bacitracin is a cyclic peptide antibiotic isolated in 1945 from a strain of Bacillus subtilis cultured from the wound of a young patient at a New York hospital, work published by Johnson, Anker, and Meleney (Science 1945). The name is a portmanteau of "Bacillus" and the patient's name. It works by binding a lipid carrier molecule (undecaprenyl pyrophosphate) that bacteria need to recycle in order to keep building their cell wall, starving the process of a required component.

Why systemic use was abandoned

The FDA approved bacitracin for injection in 1948, but significant nephrotoxicity from intramuscular use was recognized soon after, and by 1984 an FDA advisory committee concluded injectable bacitracin hadn't been shown safe and effective by modern standards. The injectable form was formally withdrawn in 2020 — a late-stage regulatory cleanup of a product that had already fallen out of real clinical use decades earlier, not a fresh safety finding.

Its real, current role

Bacitracin's toxicity is specific to systemic exposure — applied to the skin, it isn't significantly absorbed, and it remains a genuinely useful topical antibiotic. It has been a standard ingredient (alongside neomycin and polymyxin B) in over-the-counter triple-antibiotic ointments since the 1950s, a role it still fills today.