Fleming, Sir Alexander (1881-1955), was a British bacteriologist at St. Mary's Hospital at the University of London. In 1928, he discovered the germ-killing power of the green mold, Penicillium notatum, from which the life-saving antibiotic, penicillin, was first purified. For his discovery, Fleming shared the 1945 Nobel Prize in medicine with British scientists Howard Florey and Ernst B. Chain. Florey and Chain helped develop the use of this drug.

The discovery and development of penicillin opened a new era for medicine, and World War II (1939-1945) provided an opportune field trial for the drug. Fleming discovered penicillin accidentally when he saw that a bit of mold growing in a culture plate in his laboratory had destroyed bacteria around it.

Excerpt from the "Fleming, Sir Alexander" article, The World Book Encyclopedia © 1999