Index >> Bacterial Cheomotherapy >>Anitibiotics

The Penicillium colony was surrounded by a clear zone of inhibition. Fleming named the freely diffusible substance produced by the mould colony as penicillin, He showed that this substance was highly active against gram positive bacteria, and had low toxicity to animals. Penicillin was, however, unstable, and early attempts to extract it failed.

In 1940 Florey and Chain reexamined penicillin and isolated an impure but highly active solid preparation. Following the, evidence of its clinical usefulness in 1941, a large scale research programme was mounted in Britain and the U.S.A pure penicillin was isolated, and the methods far producing it on a large scale were established. The main impetus behind the programme was to prevent the infection of war wounds.

Same 2,000 antibiotic substances have been isolated and studied; of which about 50 are useful clinically. Many others are not satisfactory far clinical application as they are too toxic for internal use, but are useful for other purposes. They vary conside­rably in their chemistry, mode of action, and spectrum of activity.

The most important and widely used antibiotics which produced, a commercial scale are obtained from three main groups of microorganisms. A few antibiotics are obtained from some species of moulds (e. g. Penicillim). Some useful antibiotics have also been isolated from "true" bacteria, mainly from several species of the genus Bacillus. How ever, most of the antibiotics are obtained from several species of mould like bacteria of the genus Streptomyces. Some useful antibiotics which are produced on a commercial scale, along with their microbial source, chemical type, antimicrobial spectrum, and mode of action.