Penicillin, pehn uh SIHL ihn, is a powerful drug used to treat infections caused by bacteria. It was the first antibiotic (drug produced by microbes) used successfully in the treatment of serious diseases in human beings. Sir Alexander Fleming, a British scientist, discovered penicillin in 1928. Various forms of the drug have become widely available for medical use since the mid-1940's. Penicillins have played a major role in treating pneumonia, rheumatic fever, scarlet fever, and many other diseases. The development of penicillins had a tremendous impact on medicine and encouraged research that led to the discovery of many other antibiotics.

Excerpt from the "Penicillin" article, The World Book Encyclopedia © 1999