An antibiotic is a substance that is capable of stopping the growth of, or destroying, bacteria and other microorganisms which cause bacterial disease. Many antibiotics are themselves produced by microorganisms (bacteria and molds). Antibiotics are germicides that are safe enough to be swallowed or injected into the body.


History of antibiotics

Louis Pasteur noted the effect and Alexander Fleming first showed that the mold Penicillium notatum produced penicillin, a substance able to destroy certain bacteria. It was not until 1940 that Howard Florey and Ernst Chain were able to manufacture sufficient penicillin for clinical use.


The isolation of streptomycin by Albert Schatz (1943), a graduate student in the laboratory of Selman Waksman, of Gramcidin (from tyrothricin) by Dubos, and of the tetracyclines and Cephalosporins, were among early discoveries of antibiotics useful in treating human infection. Semi-synthetic antibiotics, in which the basic molecule is chemically modified, have increased the range of naturally occurring substances. Because some bacteria, once sensitive to certain antibiotics, have now become resistant to them, there is a constant search for new antibiotics.


The action of antibiotics

The introduction of antibiotics, from about the time of World War II, has revolutionized medical science, making possible the virtual elimination of once widespread and often fatal diseases, including typhoid fever, plague, and cholera. Some antibiotics are selective – that is, effective against specific microorganisms; those effective against a large number of microorganisms are known as broad-spectrum antibiotics.


The mode of action of antibiotics ranges from preventing cell-wall synthesis to interference with protein and nucleic acid metabolism. Bacteria resistant to antibiotics either inherently lack susceptibility to their mode of action or have acquired resistance by adaptation (e.g., by learning to make substances which inactivate an antibiotic). Each group of antibiotics has its own particular value and side effect, and antibiotics may induce allergy. Many antibiotics are effective by mouth but injection may e more suitable; topical application can also be used.


Antibiotics do not fight infections caused by viruses, such as colds, flu, most coughs and bronchitis, and sore throats, unless caused by strep.

See also antiseptic.


Antibiotic resistance









Any use of antibiotics, whether appropriate (as in the case of bacterial infections) or not (as in the case of viral infections against which antibiotics are ineffective), promotes the development of antibiotic-resistant bacteria. Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply. Repeated and extensive use of antibiotics are the primary causes of the increase in drug-resistant bacteria.



