LYCOS RETRIEVER 
Antibiotics: Penicillins
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Disease-causing microbes thwart antibiotics by interfering with their mechanism of action. For example, penicillin kills bacteria by attaching to their cell walls, then destroying a key part of the wall. The wall falls apart, and the bacterium dies. Resistant microbes... either alter their cell walls so penicillin can't bind or produce enzymes that dismantle the antibiotic.
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Today, there are hundreds of derivatives of penicillin that have been developed, including the semi-synthetic compound ampicillin that appears on the banner above, as well as a wide range of other antibiotics. Indeed, shortly after the introduction of penicillin to the world, René Dubos, an American scientist, found that a soil bacterium was able to render pneumococcus bacteria innocuous, and his further efforts revealed that a substance dubbed tyrothricin derived from the bacterium was actually able to combat an impressive array of infectious bacteria. Around the same time, American microbiologists Selman Waksman and Albert Schatz isolated streptomycin and a variety of other bacteria-fighting agents from the microbe Streptomyces griseus. These and additional antibiotics that have since been developed are responsible for saving innumerable lives and improving the quality of life for countless others.
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Traditionally, antibiotics were derived from natural compounds. Many organisms (including various species of fungi) produce substances that destroy bacteria and ... prevent infection. Penicillin, for example, is made from mold. Today, antibiotics such as fluoroquinolones are synthetic – meaning they are neither naturally occurring nor derived from natural compounds.
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Some people are allergic to antibiotics, particularly penicillins, and can develop Side effects such as a rash, swelling of the face and tongue, and difficulty breathing when they take them. Always tell your doctor or pharmacist if you have had an allergic reaction to an antibiotic; sometimes the reaction can be serious or even fatal. This is called an anaphylactic reaction.
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After penicillin was discovered, the search for additional antibiotics focused on the many fungi and bacteria that call the soil home. One particular family of micorbe grabbed the attention of scientists, the actinomycetes. This mouthful of a name comes from the ancient Greek words for “ray fungi.”
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The combination of amoxicillin and clavulanic acid specifically addresses the problem with Staphylococci: the beta-lactamase enzyme and penicillinases that destroys penicillin antibiotics. Clavulanate protects the amoxicillin by binding to these bacterial enzymes so they cannot destroy the beta-lactam ring structure that makes the penicillin molecule so effective. In short, combining clavulanic acid and amoxicillin allows this medication to kill Staphylococci while ordinary amoxicillin would be ineffective.
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Penicillins