Strep throat has become harder to fight using penicillin or amoxicillin, but that's not because the Streptococci have developed a resistance to those drugs. Instead, more than 50 percent of children have bacteria in their throats that protect strep germs. New versions of antibiotics called cephalosporins are targeting the other bacteria, improving the odds of successful treatment fivefold. read the full story ... BACKGROUND: Researchers at the University of Rochester Medical Center have found that a short treatment of a newer class of antibiotics is more effective than the traditional 10-day dose of older antibiotics like penicillin and amoxicillin to treat strep throat. The Rochester scientists reviewed over 47 studies over the past 35 years involving more than 11,000 children and found that 25 percent of children treated for strep throat with penicillin ended up back in the doctor's office within three weeks. HOW ANTIBIOTICS WORK: Infections are caused by single-celled organisms called bacteria, which can sometimes evade the body's immune system and begin reproducing. Antibiotics kill those harmful bacteria in various ways, such as preventing a bacterium from turning glucose into energy, or preventing it from construct a cell wall. The bacteria die instead of reproducing. Antibiotics are like selective poisons, because they target bacteria and not the body's own cells. They are not effective against viruses, however. Unlike bacteria, a virus isn't a living, reproducing lifeform, just a piece of DBA or RNA. A virus injects its DNA into a living cell and the cell itself reproduces more of the viral DNA. There is nothing to "kill," so antibiotics don't work on viruses. ABOUT STREP THROAT: Most sore throats are caused by viruses and generally clear up without medical treatment. Strep throat is an infection caused by a type of bacteria, and thus needs treatment with antibiotics. Symptoms include fever, stomach pain and red swollen tonsils. The bacteria can be transferred to others by sneezing, coughing or shaking hands. A doctor will usually take a throat culture to test for strep throat. Lack of treatment can lead to other health problems, such as rheumatic fever (which can damage the heart), scarlet fever, blood infections or kidney disease. DRUG RESISTANCE: Bacteria are highly adaptive, and over time they naturally develop resistance, protecting them from incoming germs (and antibiotics) and making them harder to kill. Repeated exposure to penicillin and amoxicillin can result in a throat full of bacteria that can shield strep germs from the older drugs. The surviving bacteria then reproduce more and become more dominant. Sometimes parents discontinue antibiotic medication prematurely when their children begin to feel better, so the strep germ isn't entirely killed off, leading to much more severe infections requiring the use of even stronger drugs later on.