Antibiotics

Antibiotics are chemicals used to fight diseases caused by pathogens such as bacteria, fungi, or protozoa. Only a few antibiotics are effective against just a few viruses. Antibiotics can be used to fight infections because they are toxic to specific microbes. They may be prescribed to prevent infection when the immune system is impaired, or when there is a risk of endocarditis (inflammation of the lining of the heart). Before the advent of modern antibiotics, many patients experienced a uniform progression of the disease to the death. Antibiotics were originally produced from selected mold and fungi found in the earth, air, or water.

Since the 1930s, thousands of antibiotics have been found in nature; however, only a few (over 60) have been found to be safe for use as medicines. Most modern antibiotics are made synthetically by chemical means. Millions of tons of antibiotics are manufactured every year in a process that brews a culture of the microbe that produces the chemical that is the active agent in fighting a disease. After the antibiotic broth is filtered, the antibiotic molecules are combined with a resin that is washed to collect the pure antibiotic crystals.

In the late 1800s, a Danish bacteriologist, Hans Gram, classified bacterial infections as either gram positive (G+) or as gram negative (G-). Bacteria in these categories are sensitive to some drugs, and not to others. If an antibiotic fights only a few bacteria infections, it is called a limited-spectrum drug. If it fights a wide variety of bacteria that are both G+ and G-, it is called a broad-spectrum antibiotic. Bactericidal antibiotics are drugs that kill bacteria by causing a disruption in its cell walls, causing the bacterial cell wall to turn into water and allowing water to flood the cell. It then explodes, killing the bacteria. They do not have any affect upon human tissue. Other antibiotics are bacteriostatic drugs, which work by disrupting the growth of bacteria. This allows the immune system to have time for fighting successfully the infection. The most common forms of antibiotics include aminoglycosides, macrolides, penicillins, tetracyclines, and cephalosporins. Each works in a different way.

Antibiotics are manufactured by “brewing” a culture of the microbe that produces the active disease-fighting agent.

The aminoglycosides include drugs such as gentamicin, anikacin, and tobramycin, which prevent bacteria from producing protein; however, they can damage internal ear nerves and the kidneys. Macrolides also disrupt protein production by bacteria. Erythromycin, a macrolide, can cause bowel discomfort.

Sir Alexander Fleming discovered penicillin in 1928. Many kinds of bacteria are destroyed with penicillin drugs, which destroy bacteria cell walls. However, it can cause side effects ranging from a rash or fever, to life-threatening allergic reactions [Page 57](anaphylaxis). Tetracyclines can destroy both bacteria and other organisms, and prevent the production of protein in many germs. However, side effects such as gastric discomfort, sensitivity of skin to sunlight, liver damage, or kidney damage may occur. The cephalosporins, which disrupt bacteria cell wall formation, are antibiotics that are effective against a wide range of bacteria. Cefaclor is a commonly prescribed cephalosporin. At times, physicians will prescribe a combination of antibiotics in order to ensure the destruction of the infectious bacteria and to reduce the risk of drug resistance. This can happens if a bacteria simply mutates, or if it is able to develop a growth mechanism that allows it to grow unaffected by the drug. Or, the bacteria may produce an enzyme that neutralizes the drug.

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