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Antibiotic Classes, Antibiotic Resistance

Antibiotics are natural or synthetic compounds that kill bacteria. Antibiotics are not active against viruses.

There are many different antibiotics that have different bacterial targets. Some antibiotics are specific in their activity, affecting only one or a few types (genera) of bacteria. Other antibiotics, such as penicillin, are active against a wide variety of bacteria. Such antibiotics are described as being "broad spectrum" antibiotics.

The first antibiotic discovered was penicillin. Before the discovery of penicillin by Sir Alexander Flemming (1881-1955) in 1928, bacterial infections were difficult to fight. Illnesses such as pneumonia, tuberculosis, and typhoid fever were untreatable, and bacterial infections that nowadays are minor inconveniences could become life threatening. Following the discovery of penicillin, many environmental sites were examined for compounds that exhibited anti-bacterial activity, resulting in the discovery of several naturally occurring antibiotics. As the molecular basis of activity of these antibiotics became known, antibiotics could be chemically synthesized with the ability to target specific sites on the bacterial surface, or inside bacteria.

Antibiotics can be produced by some bacteria and various eukaryotic organisms, such as plants. The antibiotics serve to protect the organism from other bacteria. Such antibiotics are typically found by screening a bacterial extract against other bacteria, and looking for inhibition in the growth of the target bacteria. Pharmaceutical companies have automated this screening process, so that thousands of samples can be examined each day.

Antibiotics can also be made by customizing a compound to a selected target on the bacterial surface or inside the bacterial cell. Molecular sequencing technology and computerized three-dimensional image simulation is extensively used in this antibiotic design process.

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