Alexander Fleming Discovers Penicillin

Scottish bacteriologist Alexander Fleming (1881–1955) returned from vacation to his laboratory at St. Mary's Hospital in London in September 1928 to find a mold, Penicillium notatum, contaminating a bacterial culture and creating a bacteria-free zone around it. He identified the mold's antibacterial secretion and published his findings in 1929. Howard Florey and Ernst Chain developed penicillin into a usable antibiotic by 1940–1941, enabling mass production in time for the Second World War. Fleming, Florey, and Chain shared the Nobel Prize in Physiology or Medicine in 1945. Penicillin inaugurated the antibiotic era.