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233 lines
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<20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20>
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<20><> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><> <20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD>
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<EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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<20><><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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<20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD> <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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ARRoGANT CoURiERS WiTH ESSaYS
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Grade Level: Type of Work Subject/Topic is on:
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[ ]6-8 [ ]Class Notes [Essay on Antibiotics ]
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[ ]9-10 [ ]Cliff Notes [ ]
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[x]11-12 [x]Essay/Report [ ]
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[ ]College [ ]Misc [ ]
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Dizzed: 10/94 # of Words:1664 School: ? State: ?
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>>Chop Here><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>><3E><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
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ANTIBIOTICS
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Antibiotics have played a major role in our society thanks to Sir
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Alexander Fleming's careful observations in 1928. Without it, many lives
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would be in danger due to infectious diseases.
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Antibiotics are chemical substances produced by various species of
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microorganisms and other living systems that are capable in small
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concentrations of inhibiting the growth of or killing bacteria and other
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microorganisms. These organisms can be bacteria, viruses, fungi, or
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animals called protozoa. A particular group of these agents is made up of
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drugs called antibiotics, from the Greek word anti ("against") and bios
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("life"). Some antibiotics are produced from living organisms such as
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bacteria, fungi, and molds. Others are wholly or in part synthetic - that
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is, produced artificially.
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Penicillin is perhaps the best known antibiotic. Its discovery and
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later development is among mankind's greatest achievements. Antibiotics
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have enabled the medical profession to treat effectively many infectious
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diseases, including some that were once life-threatening.
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How Antibiotics Work ?
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Antibiotics can be bacteriostatic (bacteria stopped from multiplying)
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or bactericidal (bacteria killed). To perform either of these functions,
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antibiotics must be brought into contact with the bacteria.
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It is believed that antibiotics interfere with the surface of bacteria
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cells, causing a change in their ability to reproduce. Testing the action
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of an antibiotic in the laboratory shows how much exposure to the drug is
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necessary to halt reproduction or to kill the bacteria. Although a large
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amount of an antibiotic taken at one time might kill the bacteria causing
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an illness, such a dose usually would make the person suffer from illness
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caused by the drug. Therefore, antibiotics are given in a series of
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smaller amounts. This assures that the bacteria are either killed or
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reduced enough in numbers so that the body can repel them. When too little
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antibiotic is taken, bacteria can often develop methods to protect
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themselves against it . The next time the antibiotic is needed against
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these bacteria, it will not be effective.
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Taking in Antibiotics.
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To work against infecting organisms, an antibiotic can be applied
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externally, such as to a cut on the skin's surface, or internally, reaching
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the bloodstream within the body. Antibiotics are made in several forms and
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given in different ways.
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Topical. Topical application means "to a local area" such as on the
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skin, in the eyes, or on the mucous membrane. Antibiotics for topical use
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are available in the form of powders, ointments, or creams.
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Oral. Tablets, liquids, and capsules are swallowed. The antibiotic
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is released in the small intestine to be absorbed into the bloodstream.
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Troches, or lozenges, are allowed to dissolve in the mouth, where the
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antibiotic is absorbed through the mucous membrane.
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Parenteral. Applications outside the intestine are called parenteral.
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One form is an injection, which can be subcutaneous (under the skin),
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intramuscular (into a muscle), or intravenous (into a vein). Parenteral
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administration of an antibiotic is used when a physician requires a strong,
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quick concentration of the antibiotic in the bloodstream.
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Manufacture.
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Natural. At one time all antibiotics were made from living organisms.
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This process, known as biosynthesis, is still used in the manufacture of
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some antibiotics. It is actually the organisms that manufacture the
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antibiotic. The people involved merely provide favorable conditions for
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the organisms to do the work and then they collect the drug. For example,
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mold organisms are placed in a medium (a substance used for the growth of
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microorganisms) such as corn steep liquor to which milk sugar has been
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added. This forms a broth that is put into a tank, which is kept at a
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temperature of 25<32>C and shaken for more than 100 hours. The mold organisms
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grow rapidly in this warm soup, producing penicillin as they do so. The
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penicillin is later extracted.
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Synthetic. All penicillin types have an identical chemical nucleus
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called a ring. The chemical chain that is attached to the ring is
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different in each type. By changing the molecules of the chain, scientists
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devise drugs with potentially different effects on different organisms.
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Some of these drugs are useful in treating infections, some are not.
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Pharmaceutical manufacturers now use computer-generated images of the
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rings and experiment with an endless variety of possible chains.
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Researchers have developed antibiotics with long half- lives (period of
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effectiveness), which allow taking the medication once in 24 hours instead
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of every few hours. The newer antibiotics are also more effective against
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a wider range of infections than were earlier drugs.
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Varieties of Antibiotics.
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There are dozens of antibiotics. The following are in common
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use:
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Penicillins. The various types of penicillins make up a large group
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of antibacterial antibiotics of which only those from benzyl penicillin are
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naturally produced from molds. Penicillin G and ampicillin are in this
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class. Another penicillin, called piperacillin, has been shown to be
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effective against 92 percent of infections without causing serious side
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effects. Penicillins are often given in combination with some of the
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following categories of drugs.
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Cephalosporins. Similar to the penicillins, cephalosporins are often
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given when a sensitivity (allergic reaction) to the former is known or
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suspected in a patient. Cefotaxime sodium is a kind of cephalosporin that
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is very effective in combating deep infections such as those that occur in
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bones and those resulting from surgery.
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Aminoglycoside. Aminoglycosides include streptomycin and neomycin.
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These drugs are used to treat tuberculosis, bubonic plague, and other
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infections. Because of potentially serious side effects, such as
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interference with hearing and their ability to make one sensitive to
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sunlight, these drugs are given with caution.
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Tetracyclines. Tetracyclines are effective against pneumonia, typhus,
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and other bacteria-caused illness but can harm the function of the liver
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and kidneys. Tetracycline in a special gel base is used to treat many eye
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infections.
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Macrolides. Macrolides are often used in patients who appear to be
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sensitive to penicillin. Erythromycin is the best known medicine in this
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group.
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Polypeptides. The class of antibiotics called polypeptides is quite
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toxic (poisonous) and is used mostly on the surface of the skin
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(topically). Bacitracin is in this category.
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Resistance and Side Effects.
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An antibiotic acts by limiting or stopping (and therefore
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killing) the growth of a specific microorganism. It probably accomplishes
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this by interfering with the wall of the bacteria cell at which it is
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targeted while at the same time having little effect on the body's normal
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cells.
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When one is exposed continually to an antibiotic for an illness of
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long duration (such as rheumatic fever), the targeted bacteria may develop
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its own defense against the drug. An enzyme that can destroy the drug may
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be produced by the bacteria, or the cell wall can become resistant to being
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broken by the action of the antibiotic. When this happens, and it does
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most frequently in response to long or frequent treatment with penicillin
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or streptomycin, the patient is said to be "fast" against the drug. For
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example, one may be penicillin-fast, meaning penicillin is no longer able
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to help fight the infection and another type of antibiotic must be given.
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Allergic reactions to antibiotics are usually seen as rashes on the
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skin, but severe anemia (too few red blood cells), stomach disorders, and
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deafness can occasionally result. It was once thought that allergic
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reactions to antibiotics - penicillin in particular - were frequent and
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permanent. Recent studies suggest, however, that many people outgrow their
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sensitivity or never were allergic. The large number of antibiotics that
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are now available offers a choice of treatment that can, in most instances,
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avoid allergy-causing drugs.
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It is well to remember that all drugs can cause both wanted and
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unwanted effects on the body. The unwanted ones are called side effects,
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and these must be balanced against the effects desired in determining if a
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particular drug will do more harm than good. It is a fact that all drugs
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have the potential to be both beneficial and harmful.
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History and Future.
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The years between 1928 and 1940 were the most fruitful in the
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discovery and development of antimicrobial drugs. In 1928 Sir Alexander
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Fleming, a British bacteriologist, noticed that a mold growing in one of
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his laboratory cultures was able to destroy that culture's bacteria. Since
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the mold that produced the substance that killed the bacteria was a species
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of Penicillium, he named the germ-killing substance penicillin. The first
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use of an antibiotic, however , is not known, as folk medicine has used
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various molds to fight infections throughout history. In 1935 a German
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chemist, Gerhard Domagk, discovered the first sulfa drug, prontosil. In
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1941 penicillin was used to treat serious infections. The results were
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dramatic because patients who received the drug made rapid and complete
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recoveries. Bacitracin, chlortetracycline, and streptomycin, naturally
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occurring antibiotics, were discovered by 1948. The penicillin ring was
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finally isolated in 1959 by british and united States scientists, and the
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way was open for the development of penicillin was the beginning of an era
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that has been called the golden age of chemotherapy. Since 1948, a large
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number of substances that inhibit or kill bacteria have been discovered.
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Another use of antibiotics is as additives to the feed of animals.
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Chickens and beef cattle, for example, can be fed with these additives for
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better weight gains and to speed their growth.
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Current work in antibiotics is largely in the area of viruses.
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Although some antivirals are available, most have toxic effects so severe
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that they can be used only in life-threatening diseases where the negative
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effects are the lesser danger. Preliminary studies, however, are reporting
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success in the development of safer antiviral drugs, and their use should
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be possible within the near future. Bibliography
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1. Pharmaceutical Preparations, Except Biologicals, 1978, Current
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Industrial Reports, Series MA28(78)-1, U.S. Department of Commerce,
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Bureau of the Census, Washington, D.C.
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2. Synthetic Organic Chemicals, United States Production and
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Sales of Medicinal Chemicals, U.S. Tariff Commission (1972-73)
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United States International Trade Commission (1974-75), U.S.
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Government Printing Office, Washington, D.C.
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3. L.S. Goodman and A. Gilman, The Pharmacological Basis of
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Therapeutics, 5th ed., Macmillan Publishing Co., New York,
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1975.
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