Penicillin, the first true antibiotic because it is a natural microbial product, was first discovered in 1896 by a twenty-one-yearold French medical student named Ernest Duchesne. His work was forgotten until Alexander Fleming accidentally rediscovered penicillin in 1928.
After returning from a weekend vacation, Fleming noticed that a Petri plate of Staphylococci also had mold growing on it and there were no bacterial colonies surrounding it. Although the precise events are still unclear, it has been suggested that a Penicillium notatum spore had contaminated the Petri dish before it had been inoculated with the staphylococci. The mold apparently grew before the bacteria and produced penicillin. The bacteria nearest the fungus were lysed. Fleming correctly deduced that the mold produced a diffusible substance, which he called penicillin. Unfortunately, Fleming could not demonstrate that penicillin remained active in vivo long enough to destroy pathogens and he dropped the research.

In 1939 Howard Florey and Ernst Chain, professors at Oxford University, obtained the Penicillium culture from Fleming and set about purifying the antibiotic. Norman Heatley, a biochemist, was enlisted to help. He devised the original assay, culture, and purification techniques needed to produce crude penicillin for further experimentation. When purified penicillin was injected into mice infected with streptococci or staphylococci, almost all the mice survived. Florey and Chain’s success was reported in 1940, and subsequent human trials were equally successful. Fleming, Florey, and Chain received the Nobel Prize in 1945 for the discovery and production of penicillin.

The discovery of penicillin stimulated the search for other antibiotics. Selman Waksman, while at Rutgers University, announced in 1944 that he and his associates had found a new antibiotic, streptomycin, produced by Streptomyces griseus. This discovery arose from the careful screening of about 10,000 strains of soil bacteria and fungi. The importance of streptomycin cannot be understated, as it was the first drug to successfully treat tuberculosis. Waksman received the Nobel Prize in 1952, and his success led to a worldwide search for other antibiotic-producing soil microorganisms. Chloramphenicol, neomycin, oxytetracycline, and tetracycline were isolated from other Streptomyces species by 1953

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