Sir Alexander Fleming (b. Aug. 6, 1881, Darvel, Scotland-d. March 11, 1955, London, England) was a Scottish physician and researcher who is best known for discovering the first antibiotic, Penicillin. Fleming enrolled at St Mary's Hospital Medical School in London. He served throughout World War I as a captain in the Royal Army Medical Corps. He was a professor at St Mary's both before and after the war.
During World War I, Fleming witnessed the death of many soldiers from sepsis resulting from infected wounds. In 1928, Fleming returned to his lab after a family holiday and noticed that one culture was contaminated with a fungus, and that the colonies of staphylococci immediately surrounding the fungus had been destroyed, whereas other staphylococci colonies farther away were normal. This accident became the first penicillin. Along with Howard Florey and Ernst Boris, Fleming received the 1945 Nobel Prize in Physiology or Medicine for this research.