bacitracin

bacitracin, antibiotic produced by a strain of the bacterial species Bacillus subtilis. It is widely used for topical therapy such as for skin and eye infections; it is effective against gram-positive bacteria, including strains of staphylococcus that are resistant to penicillin (see Gram's stain). Bacitracin is toxic to humans and is no longer used internally.

Bacitracin is a mixture of related cyclic polypeptides produced by organisms of the licheniformis group of Bacillus subtilis var Tracy, isolation of which was first reported in 1945. The drug's unique name derives from the fact that it was isolated from a girl named Tracy:

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.

As a toxic and difficult-to-use antibiotic, bacitracin doesn't work well orally. However, it is very effective topically. Its action is on gram positive cell walls.

Bacitracin is synthesised via the so-called nonribosomal peptide synthetases (NRPSs), which means that ribosomes are not involved in its synthesis.

Mechanism of action

Bacitracin interferes with the dephosphorylation of the C₅₅-isoprenyl pyrophosphate, a molecule which carries the building blocks of the peptidoglycan bacterial cell wall outside of the inner membrane .

Clinical use

Bacitracin is used in human medicine as a polypeptide antibiotic and is "approved by the FDA for use in chickens and turkeys."

As bacitracin zinc salt, and in combination with other topical antibiotics (usually polymyxin B and neomycin), it is used in ointment form for topical treatment of a variety of localized skin and eye infections, as well as for the prevention of wound infections. In the United States a popular brand name Neosporin contains Bacitracin as one of its antibiotic agents along with Neomycin and Polymyxin B. Bacitracin can also be bought in pure form for those with allergies.

It is also commonly used as an aftercare antibiotic on tattoos. It is preferred over Neosporin because of its fewer ingredients, which lowers chances of an allergic reaction.

In infants, it is sometimes administered intramuscularly for the treatment of pneumonias. This formulation is sold under the brand name Baciim.

Clinical Note: This is a good alternative to Silver sulfadiazine (Silvadene) for burn patients with Sulfa-Allergy.

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