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Chances are you or somebody you know had a sore throat recently. Most sore throats are caused by viral infections. But some are caused by bacteria like streptococci. On occasion, sore throats caused by streptococci can lead to rheumatic fever, an illness which can cause pain in the joints and severe damage to heart valves. When examining a patient with a sore throat, a doctor does a throat culture to see if streptococcus is the responsible germ. This is done by wiping a cotton swab on the patient's throat and sending the sample to a laboratory. With the lab test results, the doctor can identify the causative germ and, if it is a bacterium, decide which antibiotic should be prescribed to help kill it. Antibiotics, once considered miracle drugs, have sadly been losing ground in the fight against the same disease-causing bacteria that they routinely vanquished in the past. Because bacteria grow rapidly, a single cell can potentially produce millions of new cells each day. As they divide and reproduce, these cells have a natural tendency to change or mutate. Since the 1950s, due in part to the improper use of antibiotics, mutations have led to bacteria developing traits that make them more resistant to antibiotics and thus more of a threat to public health. Through a complex process that involves the exchange of genetic information, some bacteria can even pass resistance along to unrelated strains of bacteria. As people travel around the world they can spread resistant bacteria to other areas, further magnifying the extent of the problem. Antibiotics kill bacteria or arrest bacterial growth in a number of ways. Some, such as the quinolones and Rifampin, attack bacteria by interfering with their ability to divide. Others, such as the tetracyclines or aminoglycosides, prevent the manufacture of certain proteins essential to the bacteria. Penicillin antibiotics attack the ability of the bacterium to construct its cell wall. Through mutation, however, certain bacteria have acquired the ability to make a protein called penicillinase that destroys penicillin. Fortunately, scientists have been able to synthesize or make new antibiotics that penicillinase cannot destroy. Antibiotics frequently are viewed as a sure cure for whatever ails us and may be requested when they aren't necessary. For example, antibiotics don't work against diseases like the flu or sore throats caused by viruses. Inappropriate use contributes to the resistance problem. To stop this trend, you should take antibiotics only when needed. The proper antibiotic should be chosen and used exactly as directed. Even though you may feel better after taking the antibiotic for only a few days (since most of the bacteria causing the infection are killed), you should complete the entire recommended course for the medication to insure that all the germs are eliminated. How do microbiologists determine which antibiotics are capable of killing particular bacteria? What is the difference between prescription drugs and over-the-counter (OTC) medications? Which bacteria are "good" bacteria, and what importance do they play in our lives?