Microbiology

Microbiology Study Guide

or cell membrane of the bacteria and interfere with enzymes of the bacteria. In contrast, the bacteriostatic antibiotics, like aminoglycosides, macrolides, and tetracyclines, aim to attach the protein synthesis of the bacteria. Another way of categorizing antibiotics is on the basis of specificity of the target. Antibacterial antibiotics that have a narrow spectrum are designed to target only a specific range of bacteria, like gram-negative or gram-positive bacteria. In contrast, antibacterial antibiotics with a broad spectrum cover a wider range of bacteria. The Problem of Antibiotic Resistance It is very likely that bacteria present in the body resist the antibacterial antibiotics and drugs. This may be due to that fact that bacterial strains have a high capacity to survive high doses of these drugs. The outcome of this is the superior growth of resistant bacteria, but fortunately, the growth is reduced by the intake of the drug. During horizontal gene transfer, the resistance to antibacterial drugs may also occur. This has become an important reason why even the high efficacy drugs, like penicillin and erythromycin, have been less effective now as the bacterial strains have developed resistance against them. The development of high resistance by the bacterial strains leads to an imposition of biological cost. These species, also known as superbugs, have now become activated in the system and cause infections and diseases. For instance, the bacterial strains that cause tuberculosis have become resistant to the previous antibacterial therapies, and hence, pose new challenges to develop new and more effective drug therapies. Antibiotic Sensitivity The vulnerability of bacteria to antibiotics is known as antibiotic sensitivity. Antibiotic sensitivity involves finding the specific antibiotic that will be most effective in treating the infection or disease caused by bacteria. The method generally employed to test antibiotic sensitivity is the Kirby-Bauer method. With this test, the diagnostic plate is taken on which the growth of the bacteria is present and then small wafers, including the antibiotics, are placed over it. If the outcome shows the formation of a clear ring representing the zone of inhibition around the antibiotic wafer, it indicates that the bacteria are sensitive to the antibiotic and may indicate a fall in the growth of the bacteria. Other tests that are undertaken to test antibiotic sensitivity are the Stokes method and E-test.

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