Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
Bacteria are very small, one-celled organisms (the cell being the smallest unit of a living organism) with an average size of thousandths of a millimeter. Based on their relatively simple structure, they are classified as prokaryotic cells. Prokaryotic cells have a rigid outer cell wall, very simply organized hereditary material (deoxyribonucleic acid, or DNA) floating free within the cell, and only a few other structures necessary for their survival, growth, and reproduction. Eukaryotic cells, such as those found in humans, plants, and other animals, have highly organized DNA and many more internal structures. Despite the fact that bacteria are relatively “simple,” they are still very complex living organisms.
The many types of bacteria can be divided into three categories based on their shape: coccus (round), bacillus (rod-shaped), or spirillum (spiral). Another major distinction between types of bacteria is based on the sugar and lipid (fat) composition of their cell walls. This difference can be identified through Gram staining, the result of the stain determining whether the organism is gram-positive or gram-negative. Various types of bacteria may have additional structures that are useful in their identification. Capsules and slime layers are water-rich sugary materials secreted by the bacteria which cling to their surfaces and form halolike structures. Flagella are long, thin, whiplike structures found in one...
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
The medical management of the many bacterial infections and the diseases they cause begins with diagnosis. Diagnosis relies on a variety of biochemical tests that are analyzed in conjunction with the signs and symptoms exhibited by the infected individual. Treatment is then designed so that it not only eliminates the disease symptoms but also eradicates all invading bacterial organisms, thereby minimizing the chance of a recurrence of the disease. Prevention involves steps that the individual takes to avoid potential contact with infectious diseases, as well as the use of medical procedures that protect against specific bacterial diseases.
To treat a bacterial disease properly, the invading organism must be identified correctly. In some cases, symptomology can be specific enough to identify the offending bacterium, but since there are literally thousands of different types of disease-causing organisms, a systematic approach using a variety of tests is undertaken to make a definitive diagnosis. First, a specimen from the infected person is collected. This may be a blood or urine sample; a swab of the infected area, such as the throat or another skin surface; or a secretion, such as sputum, mucus, or pus. Since human bodies are normally inhabited by a variety of harmless bacteria, the individual types of bacteria are isolated in pure cultures, in which each bacterium present is of the same type. The pure cultures are then...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Bacteria were first described as “animalcules” by the Dutch scientist Antoni van Leeuwenhoek in 1673 after he observed them in water-based mixtures with a crudely designed microscope. In 1860, Louis Pasteur recognized that bacteria could cause the spoiling of wine and beer because of the by-products of their metabolism. Pasteur’s solution to this problem was heating the beverages enough to kill the bacteria, but not change the taste of the drink—a process known as pasteurization, which is used today on milk and alcoholic beverages. In addition, Pasteur settled a long-standing debate on the origin of living things that seemed to arise spontaneously in fluids exposed to the air. He demonstrated that these life-forms were seeded by contaminating bacteria and other microorganisms found in the air, in fluids, and on solid surfaces. Pasteur’s work led to standard practices in laboratories and food processing plants to prevent unwanted bacterial contamination; these practices are referred to as aseptic techniques.
Prior to the late nineteenth century, deaths from wounds and simple surgeries were quite common, but the reason for these high mortality rates was unknown. In the 1860’s, Joseph Lister, an English surgeon, began soaking surgical dressings in solutions that killed bacteria, and the rate of survival in surgical and wound patients was greatly improved. In 1876, Robert Koch, a German physician, discovered...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Biddle, Wayne. A Field Guide to Germs. 2d ed. New York: Anchor Books, 2002. This comprehensive book is easily accessible to the nonspecialist and includes a discussion of nearly every virus, bacterium, and fungus known to cause human and nonhuman animal disease. The history of the microbe and the treatment of diseases are included.
Forbes, Betty A., Daniel F. Sahm, and Alice S. Weissfeld. Bailey and Scott’s Diagnostic Microbiology. 12th ed. St. Louis, Mo.: Mosby/Elsevier, 2007. A well-organized text that is accessible to the general reader. Describes in detail methods for the isolation and identification of microorganisms, in particular diagnostic procedures for the identification of bacterial infectious diseases.
Frank, Steven A. Immunology and Evolution of Infectious Disease. Princeton, N.J.: Princeton University Press, 2002. Blends research from molecular biology, immunology, pathogen biology, and population dynamics to discuss how and why parasites vary to escape recognition by the immune system, vaccine design, and the control of epidemics.
Joklik, Wolfgang K., et al. Zinsser Microbiology. 20th ed. Norwalk, Conn.: Appleton and Lange, 1997. This is the bible of microbiology, with a heavy emphasis on medical microbiology. Features a detailed analysis of the biochemistry of bacteria and other microorganisms.
Pelczar, Michael J., Jr., E. C. S. Chan, and Noel...
(The entire section is 396 words.)