Penicillin, today so taken for granted, is one of the major medical achievements of the 20th Century.

Penicillin was the first naturally-occurring antibiotic to be discovered and to be employed for medicinal purposes. However, its true potential remained stubbornly elusive for decades.

A breakthrough came in 1928 when Scottish physician Alexander Fleming accidentally allowed a fungal spore to land in an exposed petri dish containing staph bacteria. He noted the development of a zone around the fungus that was devoid of any bacteria. He theorized the fungus, identified as Penicillium notatum, had produced a substance that killed the bacteria.

But even with this, the quest to harness penicillin stalled in the 1930s. Fleming's last article on the subject appeared in 1931.

Finally in 1939, three scientists at Oxford, led by W.H. Florey, were able to prepare and test penicillin on mice. After this successful testing, the first human trial experiments were undertaken. These too were successful.

The timing was fortuitous, for England was coming under the full assault of the Nazi blitzkrieg and World War II was on the march. The United States was the first large-scale producer of penicillin, mostly because of the fears in England of such manufacturing being destroyed in German air raids.

The new drug was invaluable during the war years. Previously, wounded soldiers usually faced a greater risk of dying from infection created by the wounds than from the wounds themselves. Penicillin began to change all that.