bac·i·tra·cin 
(băs′ĭ-trāsĭn)
(băs′ĭ-trāsĭn)n.
A polypeptide antibiotic obtained from a strain of a bacterium (Bacillus subtilis) and used as a topical ointment in the treatment of certain bacterial infections, especially those caused by cocci.
[BACI(LLUS) + Trac(y I), laboratory designation of the strain of bacterium producing it (apparently from misspelling of the name of Margaret Treacy (1936?-1994), American child from whose tissue the strain was first isolated) + -IN.]