RESISTANT GERMS
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In this series:
Related topics:
Alexander Fleming, who discovered penicillin |
Those Resilient Germs
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What Are Antimicrobials?The antibiotic given you by a doctor falls into a class of medicines called antimicrobials. These come under the general heading "chemotherapy," which refers to the treatment of disease with chemicals. While the term "chemotherapy" is often used in connection with treating cancer, it originally appliedand still doesto the treatment of infectious diseases. In such cases it is called antimicrobial chemotherapy. Microbes, or microorganisms, are tiny organisms that can be seen only with the help of a microscope. Antimicrobials are chemicals that act against microbes that cause illness. Unfortunately, antimicrobials can also act against microbes that are beneficial. In 1941, Selman Waksman, codiscoverer of streptomycin, applied the term "antibiotic" to antibacterials that come from microorganisms. Antibiotics as well as other antimicrobials used in medical treatment are valuable because of what is called selective toxicity. This means that they can poison germs without seriously poisoning you. Actually, however, all antibiotics are at least somewhat poisonous to us too. The margin of safety between the dosage that will affect the germs and the dosage that will harm us is called the therapeutic index. The larger the index, the safer the drug; the smaller, the more dangerous. In fact, thousands of antibiotic substances have been found, but most are not useful in medicine because of being too toxic to people or to animals. The first natural antibiotic that could be used internally was penicillin, which came from a mold called Penicillium notatum. Penicillin was employed intravenously for the first time in 1941. Shortly thereafter, in 1943, streptomycin was isolated from Streptomyces griseus, a soil bacteria. In time, scores of additional antibiotics were developed, both those that are derived from living things and those that are made synthetically. Yet, bacteria have developed ways of resisting many of these antibiotics, causing a global medical problem. |
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Multidrug ResistanceThen, to their horror, medical scientists learned that bacteria exchange genes among themselves. At first it was thought that only bacteria of the same type could exchange genes. But later the very same resistance genes were discovered in completely different types of bacteria. By means of such exchanges, bacteria of various types have accumulated resistance to many different commonly used drugs. As if all of this were not enough, studies in the 1990's showed that some bacteria can become drug resistant on their own. Even in the presence of only one antibiotic, some kinds of bacteria develop resistance to multiple antibiotics, both natural and synthetic. A Foreboding FutureAlthough most antibiotics today still work in the majority of people, how effective will such drugs be in the future? The Antibiotic Paradox observes: "We can no longer expect that any infection will be cured by the first antibiotic chosen." The book adds: "In some parts of the world, limited supplies of antibiotics mean that no available antibiotic is effective. . . . Patients are suffering and dying from diseases that some predicted 50 years ago would be wiped off the face of the earth." Bacteria are not the only germs that have become resistant to drugs used in medicine. Viruses as well as fungi and other tiny parasites have also shown amazing adaptability, offering the world strains that threaten to nullify all the efforts invested to discover and produce the drugs that fight them. What, then, can be done? Can resistance be eliminated or at least contained? How can the victories won by antibiotics and other antimicrobials be preserved in a world increasingly beset by infectious diseases? |
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* "Antibiotic," as the word is commonly used, is medicine that fights bacteria. "Antimicrobial" is a more general term and includes any drug that combats disease-causing microbes, be they viruses, bacteria, fungi, or tiny parasites. # Insecticides are poisons, but so are drugs. Both have proved to be helpful as well as harmful. While antibiotic drugs may kill harmful germs, these drugs also kill beneficial bacteria. |
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Appeared in Awake! October 22, 2003 |