Milestones in Pharmaceutical History: Fleming’s Discovery of Penicillin

October is American Pharmacists Month – a time to recognize the contributions of pharmacists to health care in their communities. In their honor, we’ll be publishing a series of posts about milestones in pharmaceutical history that have immeasurably advanced drug safety and improved public health. In our first post, we celebrate the discovery of penicillin by Alexander Fleming in 1928, which launched the modern antibiotic revolution.

Fleming’s Fortunate Accident with Mold

In the late 19th century, scientists for the first time began publishing accounts of the antibacterial properties of molds, but they were unable to determine what process was causing this effect. A Scottish physician, bacteriologist, and pharmacologist, Alexander Fleming, was the first scientist not only to identify and isolate penicillin, but also to promote his findings to the scientific community and wider public.

The story goes something like this: on September 3, 1928, Fleming returned home to London after spending August on holiday with his family. Visiting his hospital laboratory, he happened to notice that an open Petri dish containing Staphylococci had been accidentally contaminated by mold. The colonies of bacteria immediately surrounding the mold had been destroyed, while other colonies farther away from the mold were thriving.

Investigating further, Fleming eventually identified the mold as Penicillium notatum (currently Penicillium chrysogenum) – the first antibiotic ever to be recognized. After several years of unsuccessful attempts to advance the drug’s development, Fleming eventually abandoned his work with penicillin. However, he did point out that it had clinical potential, both as a topical antiseptic and as an injectable antibiotic.

Penicillin’s Mass Production and Distribution

Although Fleming technically discovered penicillin, other scientists had to stabilize and purify it before it could be mass produced and distributed for general use. That work was accomplished by Howard Florey and Ernst Chain at the University of Oxford. With a deeper understanding of chemistry than Fleming, a state-of-the-art lab, and funding from the U.S. and British governments, they performed the first comprehensive studies on penicillin.

World War II accelerated the diffusion of the drug. In 1943, the War Production Board drew up a plan for the delivery of pharmaceutical-grade penicillin stocks to Allied troops fighting in Europe. To accomplish this goal, Pfizer scientist Jasper H. Kane and chemical engineer Margaret Hutchinson Rousseau developed a process known as deep-tank fermentation. By D-Day in 1944, enough penicillin had been produced to treat all the wounded in the Allied forces. 

The first chemical synthesis of penicillin occurred years later in 1957 by chemist John C. Sheehan at the Massachusetts Institute of Technology. By 1961, the production of ampicillin offered a broader spectrum of activity than the original strains of penicillin. Even further R&D yielded additional strains, including flucloxacillin, dicloxacillin, and methicillin.

Fleming’s Lasting Legacy 

Alexander Fleming was a scientist of many talents, but his discovery of penicillin sealed his lasting reputation through significantly changing the world of modern medicine. Although resistant bacteria continue to flourish in the 21st century because of over-prescription and dosing in livestock, penicillin is still used today to treat a wide range of infections caused by Streptococci, Staphylococci, Clostridium, Neisseria, and Listeria.

Ironically, in Fleming’s acceptance speech for the Nobel prize in 1945, he warned that the overuse of penicillin might, one day, lead to bacterial resistance. That day has come – perhaps sooner than he predicted. Nevertheless, his achievement is monumental. In fact, Time magazine named Fleming as one of the 100 Most Important People of the 20th century. For those of us who have suffered the onset of strep throat and found quick relief from a dose of antibiotics, I think we’d agree!

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