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Medicine History: The Queer Story of Sir Alexander Fleming’s Discovery of Penicillin


KIU, Western Campus - Today marks the 92nd anniversary of the discovery of penicillin, the first naturally occurring antibiotic drug discovered and used therapeutically.

Sir Alexander Fleming, a Scottish researcher, is credited with the discovery of penicillin in 1928. At the time, Fleming was experimenting with the influenza virus in the Laboratory of the Inoculation Department at St. Mary’s Hospital in London.

According to, a medical website, Fleming returned from a two-week vacation to find that a mold had developed on an accidentally contaminated staphylococcus culture plate. Upon examination of the mold, he noticed that the culture prevented the growth of staphylococci.

According to Wikipedia, Staphylococcus is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. 

Under the microscope, they appear spherical or round (cocci), and form in grape-like clusters. Staphylococcus species are facultative anaerobic organisms (capable of growth both aerobically and anaerobically). In ordinary terms, it grows with or without the presence of oxygen.

According to, an article published by Fleming in the British Journal of Experimental Pathology in 1929 reads, “The staphylococcus colonies became transparent and were obviously undergoing lysis (the disintegration of a cell by rupture of the cell wall or membrane) … the broth in which the mold had been grown at room temperature for one to two weeks had acquired marked inhibitory, bactericidal and bacteriolytic properties to many of the more common pathogenic bacteria.” Put simply, it means that the mold had started destroying the bacteria.

Published reports credit Fleming as saying: “One sometimes finds what one is not looking for. When I woke up just after dawn on Sept. 28, 1928, I certainly didn’t plan to revolutionize all medicine by discovering the world’s first antibiotic, or bacteria killer. But I guess that was exactly what I did.”

Fleming stopped studying penicillin in 1931 but his research was finished by Howard Flory and Ernst Chain, researchers at the University of Oxford who are credited with the development of penicillin for use as a medicine 

One of the most widely used antibiotics in the world, penicillin is used to treat and prevent a wide variety of bacterial infections. It works by stopping the growth of bacteria. 

Penicillin treats and prevents only bacterial infections. 

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