Penicillin is a β-lactam antibiotic used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms. The name "penicillin" can either refer to several variants of penicillin available, or to the group of antibiotics derived from the penicillins.Penicillin has a molecular formula R-C9H11N2O4S, where R is a variable side chain.
History
Penicillin was originally isolated from the Penicillium chrysogenum (formerly Penicillium notatum) mould. The antibiotic effect was originally discovered by a young French medical student Ernest Duchesne studying Penicillium glaucum in 1896, although his work had no lasting consequences.
It was serendipitously rediscovered by Alexander Fleming in 1928, who noticed a halo of inhibition of bacterial growth around a contaminant blue-green mould on a Staphylococcus culture. Fleming concluded that the mould was releasing a substance that was inhibiting bacterial growth. He grew a pure culture and discovered that the fungus was Penicillium notatum — he later named the bacterial inhibiting substance penicillin after the Penicillium notatum that released it.
Fleming was convinced after conducting some more experiments that penicillin could not last long enough in the human body to kill pathogenic bacteria and stopped studying penicillin after 1931. It would prove to be the discovery that changed modern medicine. In 1939, Howard Walter Florey and a team of researchers at Oxford University made significant progress in showing Penicillin's in vivo ability to kill infectious bacteria. This eventually led to commercial production of penicillin.
During World War II, penicillin made a major difference in the number of deaths and amputations caused by infected wounds amongst Allied forces. Availability was severely limited, however, by the difficulty of manufacturing large quantities of penicillin and by the rapid renal clearance of the drug necessitating frequent dosing. Penicillins are actively secreted and about 80% of a penicillin dose is cleared within three to four hours of administration........
