Penicillin: 83 Years Ago Today

Eighty-three years ago today, Sir Alexander Fleming discovered penicillin, one of the most widely used antibiotics.

Inspired by what he saw on the battlefields of World War I, he went back to his laboratory at St. Mary’s Hospital in London to develop a way to fight bacterial infections.

In 1928, he accidentally left a petri dish in which he was growing Staphylococcus aureus bacteria uncovered. Later, he noticed that there was mold growing on the plate, and around the mold, the staph bacteria were dead. Fleming isolated it and identified the mold as Penicillium notatum, a type of fungus that is similar to the mold that grows on bread. Fleming published his findings in the British Journal of Experimental Pathology in 1929, but the report didn’t garner much interest.

Then in 1938, Ernst Chain, a biochemist working with pathologist Howard Florey at Oxford University, came across Fleming’s paper while he was researching antibacterial compounds. Scientists in Florey’s lab started working with penicillin, which they eventually injected into mice to test if it could treat bacterial infections. Their experiments were successful and they went on to test it in humans, where they also saw positive results.

By 1941, there was an injectable form that could be used to treat patients, which was especially useful for soldiers fighting in World War II. 

Today, penicillin, considered the first wonder drug, is used to treat throat infections, meningitis, syphilis and other bacterial infections. It works by inhibiting enzymes involved in building bacterial cell walls and by activating other enzymes that break these protective barriers down.  Some bacteria have developed resistance to penicillin, highlighting the importance of using antibiotics carefully.

In 1945, Fleming, Chain and Florey were awarded the Nobel Prize in Physiology or Medicine for “the discovery of penicillin and its curative effects in various infectious diseases”. 

Fleming died in 1955.

For more information, read Richard Syke's paper Penicillin: from discovery to product

— Daniela Hernandez