Bacitracin
is a polypeptide antibiotic. It is a mixture of related
cyclic peptides produced by
Bacillus licheniformis bacteria, that was first isolated from the variety "Tracy I" (ATCC 10716) in 1945.
[Originally grouped under B. subtilis, but nomenclature has since changed. See ] These peptides disrupt Gram-positive bacteria by interfering with
cell wall and peptidoglycan synthesis.
Bacitracin is primarily used as a topical preparation, as it can cause kidney damage when used internally. It is generally safe when used topically, but in rare cases may cause hypersensitivity, allergy or anaphylaxis reactions, especially in people allergic to neomycin.
In 2022, it was the 323rd most commonly prescribed medication in the United States, with more than 100,000 prescriptions.
Medical uses
of bacitracin ointment for the eye]] Bacitracin is used in human medicine as a polypeptide antibiotic and is "approved by the US Food and Drug Administration (FDA) for use in chickens and turkeys," though use in animals contributes to antibiotic resistance.
As bacitracin zinc salt, in combination with other topical antibiotics (usually polymyxin B and neomycin) as an ointment ("triple antibiotic ointment," with the brand name Neosporin), it is used for topical treatment of a variety of localized skin and eye infections, as well as for the prevention of wound . A non-ointment form of ophthalmic solution is also available for eye infections.
Spectrum of activity and susceptibility data
Bacitracin is a narrow-spectrum antibiotic. It targets Gram-positive bacteria, especially those that cause skin infections. The following represents susceptibility data for a few medically significant microorganisms.
-
Staphylococcus aureus – ≤0.03 μg/mL – 700 μg/mL
-
Staphylococcus epidermidis – 0.25 μg/mL – >16 μg/mL
-
Streptococcus pyogenes – 0.5 μg/mL – >16 μg/mL
Mechanism of action
Bacitracin interferes with the dephosphorylation of C
55-isoprenyl pyrophosphate, and a related molecule known as
bactoprenol pyrophosphate; both of these lipids function as membrane carrier molecules that transport the building-blocks of the
peptidoglycan bacterial
cell wall outside of the inner membrane.
History
Bacitracin was isolated by
Balbina Johnson, a
bacteriologist at the Columbia University College of Physicians and Surgeons.
[ Its name derives from the fact that a compound produced by a microbe in young Margaret Tracy's (1936–1994)] leg injury showed antibacterial activity.
"One strain isolated from tissue debrided from a compound fracture of the tibia was particularly active. We named this growth-antagonistic strain for the patient, Tracy I. When cell-free filtrates of broth cultures of this bacillus proved to possess strong antibiotic activity and to be non-toxic, further study seemed warranted. We have called this active principle 'bacitracin'."
Bacitracin was approved by the US FDA in 1948.
Synthesis
Bacitracin is synthesised via nonribosomal peptide synthetases (NRPSs), which means that are not directly involved in its synthesis. The three-enzyme operon is called BacABC, not to be confused with BacABCDE of bacilycin synthesis.
Composition
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.["Committee for Veterinary Medicinal Products Bacitracin." Ema.europa.eu. The European Agency for the Evaluation of Medicinal Products, June 1998. Web. 18 January 2013] Bacitracin A has been found to have the most antibacterial activity. Bacitracin B1 and B2 have similar potencies and are approximately 90% as active as bacitracin A.
Society and culture
Controversies
Claims that bacitracin is a protein disulfide isomerase inhibitor are disputed by in vitro studies.