ACS Chemistry for Life

The introduction of penicillin in the 1940s, which opened up the era of antibiotics, has been recognized as one of the greatest advances in therapeutics. This dramatic medical breakthrough was a result of combined efforts in the United Kingdom and the United States. The discovery of penicillin and the initial recognition of its therapeutic potential occurred in the United Kingdom, but, due to World War II, the United States played the major role in developing large-scale production of the drug, thus making a life-saving substance in limited supply into a widely available medicine.

Antibiotics are compounds produced by bacteria and fungi which are capable of killing, or inhibiting, competing microbial species. This phenomenon has long been known; it may explain why the ancient Egyptians had the practice of applying a poultice of moldy bread to infected wounds. But it was not until 1928 that penicillin, the first true antibiotic, was discovered by Alexander Fleming, Professor of Bacteriology at St. Mary’s Hospital in London.

Returning from holiday on September 3, 1928, Fleming began to sort through petri dishes containing colonies of Staphylococcus, bacteria that cause boils, sore throats, and abscesses. He noticed something unusual on one dish. It was dotted with colonies, save for one area where a blob of mold was growing. The zone immediately around the mold – later identified as a rare strain of Penicillium notatum – was clear, as if the mold had secreted something that inhibited bacterial growth.

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Excerpted with permission, National Historic Chemical Landmarks Program
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