Which scientist discovered penicillin in 1928 after observing mould inhibit bacterial growth?

Alexander Fleming discovered penicillin in 1928 after observing mould inhibit bacterial growth.

Fleming was a Scottish bacteriologist working at St Mary’s Hospital in London. In September 1928, he noticed that a mould contaminating a staphylococcus culture had created a clear zone where bacteria failed to grow. He identified the mould as Penicillium and named the antibacterial substance penicillin.

Fleming published his findings in 1929, but penicillin was not immediately developed into a widely usable medicine. Researchers at Oxford, including Howard Florey and Ernst Chain, later developed methods for purifying and producing it. Their work helped turn Fleming’s observation into a practical treatment during the Second World War.

Fleming, Florey, and Chain shared the 1945 Nobel Prize in Physiology or Medicine. Fleming’s discovery was accidental, but recognizing and investigating the unusual result required careful scientific observation.