A Growing Resistance To Antibiotics


To Make Sure The Wonder Drugs Will Keep Working, They Must Be Used With Care.

August 24, 1999|By Susan Okie, Washington Post

You have a scratchy throat and plugged-up sinuses - worse than a cold, you think. You go to the doctor and plead for a prescription for antibiotics. In a few days, when you feel better, you stop taking the drug.

That common scenario is a major reason why infectious agents are increasingly able to fight off the miracle drugs designed to conquer them.

The rise in cases of drug-resistant tuberculosis in countries around the world is one alarming aspect of a more-general global problem: the emergence of antibiotic resistance in many kinds of disease-causing bacteria. Just last week, federal health experts said four children from Minnesota and North Dakota have died from a common staph infection that is growing increasingly resistant to the antibiotics used to treat it.

And streptococcus pneumoniae, a common cause of pneumonia and childhood ear infections, used to be exquisitely sensitive to penicillin and chemically related antibiotics. But now many strains have become harder to kill, requiring patients to take much higher doses. Some hospital strains of staphylococcus, the culprit in many skin and wound infections, have become resistant to vancomycin, a powerful antibiotic that doctors have relied on to work in such cases when all else failed.

The development of resistance to antibiotics isn't some conscious, malicious plot hatched by germs. Instead, the new strains evolve in large part because doctors and patients are misusing these drugs.

Resistant bacteria arise through a process called natural selection. When bacteria are repeatedly exposed to powerful antibiotics that kill large numbers of them, the few that possess the genetic capacity to survive are ``selected.'' They eventually multiply until they predominate, creating a new strain of bacteria that isn't responsive to standard drugs.

This process works the same way in bacteria that cause tuberculosis and in those that cause other diseases. It's also the reason some strains of the human immunodeficiency virus (HIV) are developing resistance to drugs used to treat AIDS.

Used properly, antibiotics work so well against bacterial infections that the results often seem miraculous. But that very effectiveness makes patients demand them and leads some doctors to prescribe them indiscriminately. The result is widespread overuse here and in other countries.

Researchers at the federal Centers for Disease Control and Prevention estimate that as many as a third of the approximately 150 million courses of antibiotic treatment prescribed in the United States each year may be unnecessary.

Illnesses that shouldn't be treated with antibiotics (but often trigger a prescription anyway) include the common cold, sore throats not caused by ``strep'' bacteria, most cases of bronchitis, sinus congestion not accompanied by the severe pain and fever that signal an acute infection, and fluid behind the eardrum of a child who isn't having fever and earache.

Most colds, coughs, sore throats and stuffy noses, as well as many childhood ear infections, are caused by viruses - and most viruses that invade the upper respiratory tract can't be killed by drugs. (One exception is the influenza virus, for which new antiviral drugs are becoming available, but CDC experts say they probably won't be needed in the majority of ``flu'' cases.)

``One of the things we're really trying to get across to the public is the difference between a bacterial infection that may be cured by antibiotics and viral infections that cannot be cured by antibiotics,'' said Richard Besser, a pediatrician and medical epidemiologist at the CDC.

Taking antibiotics when they're not needed isn't merely wasteful; it can be dangerous for the patient and for the community. All drugs have potential side effects. For example, many antibiotics kill off various species of bacteria that normally live in the digestive tract, sometimes leading to the overgrowth of one type, Clostridium difficile, that can produce diarrhea and intestinal inflammation.

Since the human body harbors millions of bacteria at all times, taking antibiotics also exposes those resident bacteria to natural selection, contributing to the evolution of resistant strains that might produce an infection or be passed to someone else. Some types of resistant bacteria can live on the skin or in the nose, throat or digestive tract without producing any symptoms, but may cause illness if transmitted to a vulnerable person - a newborn baby, a surgical patient or someone with a weakened immune system.

Once resistant strains of bacteria become common in a community or in a hospital, anyone may become infected - not just people who have taken many antibiotics in the past. Someone who develops drug-resistant TB, for instance, can transmit it to healthy family members, friends or health-care workers.

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