Antibiotic

An antibiotic is a drug that kills or slows the growth of bacteria. Antibiotics are one class of antimicrobials, a larger group which also includes anti-viral, anti-fungal, and anti-parasitic drugs. They are relatively harmless to the host, and therefore can be used to treat infections. The term, coined by Selman Waksman, originally described only those formulations derived from living organisms, in contradistinction to "chemotherapeutic agents", which were purely synthetic. Nowadays the term "antibiotic" is also applied to synthetic antimicrobials, such as the sulfonamides. Antibiotics are small molecules with a molecular weight less than 2000. They are not enzymes.

History

Following earlier experiments that had demonstrated interesting anti-bacterial effects from various bacterial secretions, the German scientist E. de Freudenreich in 1888 isolated a bacterial secretion and noted its antibacterial properties. Pyocyanase, secreted by Bacillus pyocyaneus, retarded the growth of other bacteria in situ and was toxic to many disease-causing bacteria. Unfortunately, pyocyanase's own toxicity and unstable character prevented its use as an effective, safe antibiotic within the human body.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

French physician Ernest Duchesne noted in his 1896 thesis that certain Penicillium molds killed bacteria. Duchesne died within a few years, and his research was forgotten for a generation. Sir Alexander Fleming (August 6, 1881 ? March 11, 1955) discovered the antibiotic substance lysozyme and isolated the antibiotic substance penicillin from the fungus Penicillium notatum. Alexander Fleming had been culturing bacteria on agar plates, one of which was ruined by an accidental fungal contamination. Rather than discarding the contaminated plate, Fleming noticed a clear zone surrounding the colony of mold. Having previously studied the ability of the enzyme lysozyme to kill bacteria, Fleming realized that the mold was secreting something that stopped bacterial growth. He knew that this substance might have enormous utility to medicine. Although he was unable to purify the compound (the beta-lactam ring in the penicillin molecule was not stable under the purification methods he tried), he reported it in the scientific literature in 1929. Since the mold was of the genus Penicillium, he named this compound penicillin.

Related Topics:
Ernest Duchesne - Penicillium - Alexander Fleming - Agar - Mold - Lysozyme - Beta-lactam - 1929

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the 1930s German researcher Gerhard Domagk investigated the antibacterial properties of certain dyes. One of these was a sulfonamide, Prontosil, which was found to be effective against infections in humans due to its conversion in the host to the active form, sulfanilimide. By today's more broad definition, this would likely qualify as the first successful use of an oral antibiotic. During the same era, René Dubos isolated tyrothricin, an antibiotic used topically for skin infections, from soil bacteria.

Related Topics:
1930 - Gerhard Domagk - Sulfonamide - Prontosil - René Dubos - Tyrothricin

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

With the increased need for treating wound infections in World War II, resources were poured into investigating and purifying penicillin, and a team led by Howard Walter Florey succeeded in producing usable quantities of the purified active ingredient which were quickly tested on clinical cases. Physicians were exhilarated at the rapid and reliable cure of conditions which had, until then, been difficult to treat, terrible to endure, and frequently fatal. Observation of other species of mold and other organisms revealed a hitherto unknown level of chemical warfare being carried out against bacteria. New antibiotics were rapidly discovered and came into widespread use, and a new era of research into the possibility of similarly "magic" chemotherapeutic cures for other diseases eventually led to successes in the field of cancer chemotherapy.

Related Topics:
World War II - Howard Walter Florey - Mold - Chemotherapy

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The discovery of antibiotics, along with anesthesia and the adoption of hygienic practices by physicians (for example, washing hands and using sterilized instruments) revolutionized medicine. It has been said that this is the greatest advance in health since modern sanitation. People in developed countries now find it hard to imagine that a simple scratch once always carried the risk of infection and death.

Related Topics:
Anesthesia - Hygienic practices - Medicine - Sanitation

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

See also Timeline of antibiotics.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Antibiotics can also be classified by the organisms against which they are effective, and by the type of infection in which they are useful, which depends on the sensitivities of the organisms that most commonly cause the infection and the concentration of antibiotic obtainable in the affected tissue.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~