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Natural Penicillins
Agents: penicillin G, penicillin V
All of us have heard of the discovery of penicillin
by Sir Alexander Fleming in 1929. Once penicillin
was isolated years later, it had a major impact
on society, particularly in the treatment of wound
infections. The importance of this discovery became
apparent during World War II, when the Allies had
access to life- and limb-saving penicillin and the
Axis did not. Unfortunately, staphylococci quickly
became resistant to penicillin, initiating the search
for new beta-lactams and leading to the confusing
array of these drugs available today. The development
of resistance has narrowed the spectrum of
effectiveness of natural penicillins considerably
over the past 60 years, such that staphylococci are
almost universally resistant to them. Occasionally
we still see an isolate of Staphylococcus aureus
that is susceptible to penicillin.
Mechanism of Action
All beta-lactams inhibit cross-linking of peptidoglycan
in the cell wall, leading to autolysis and cell
death.
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