Bacitracin is a mixture of
polypeptide antibiotics pro-duced by Bacillus
subtilis. As with penicillin, it contains a thiazolidine nucleus attached
through L-leucine to a pep-tide composed of both D- and L-amino acids. However, it
does not contain a β-lactam ring. Bacitracin
prevents cell wall synthesis by
binding to a lipid pyrophosphate carrier that transports cell wall precursors
to the growing cell wall.
Bacitracin inhibits the
dephosphorylation of this lipid carrier, a step essential to the carrier
molecule’s ability to accept cell wall constituents for transport.
gram-positive cocci, including Staphy-lococcus
aureus, streptococci, a few gram-negative or-ganisms, and one anaerobe, Clostridium difficile.
Bacitracin is primarily a topical antibiotic. Previously, it was
administered intramuscularly, but the toxicity asso-ciated with its parenteral
administration has precluded systemic use. The bacitracins are not absorbed
from the gastrointestinal tract following oral administration.
Bacitracin is highly active
against staphylococci, Strep-tococcus
pyogenes, and C. difficile. Its
high degree of activity against the
group A streptococci is used in the laboratory as a means of differentiating
between the Lancefield group A streptococci and other streptococci.
Bacitracin is well tolerated
topically and orally and is frequently used in combination with other agents
(notably polymyxin B and neomycin) in the form of creams, ointments, and
aerosol preparations. Hydro-cortisone has been added to the combination for its
an-tiinflammatory effects. Bacitracin preparations are ef-fective in the
treatment of impetigo and other superficial skin infections. However,
poststreptococcal nephritis has followed the topical treatment of im-petigo,
and therefore oral penicillin therapy is pre-ferred. Bacitracin has been used
with limited success for eradication of S.
aureus in the nares. Because of the risk of serious nephrotoxicity, the parenteral use of baci-tracin is not