We found that penicillin is produced during fungal colonization
of the salami casing in the early stages of the curing
process, in agreement with previous reports (2, 7). This is one
of the first examples of the production of an antibiotic in a
natural substrate and provides support for the role of antibiotics
as antagonists in nature (5). The penicillin in the salami
casing diffuses to the outer layer of the meat and becomes
undetectable in the salami core. Cured salami (as available in
the market) had no detectable levels of penicillin. The reason
for the decay of penicillin during the curing process is unclear,
although it may be due to inactivation by exposure of the
antibiotic to an acid pH for prolonged periods of time.