bacitracin (băsˌĭtrāˈsĭn) [key], 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.
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