Battle of the Bugs: Fighting Antibiotic Resistance. (Cover Story)

Article excerpt

Ever since antibiotics became widely available about 50 years ago, they have been hailed as miracle drugs--magic bullets able to destroy disease-causing bacteria.

But with each passing decade, bacteria that resist not only single, but multiple, antibiotics--making some diseases particularly hard to control--have become increasingly widespread. In fact, according to the Centers for Disease Control and Prevention (CDC), virtually all significant bacterial infections in the world are becoming resistant to the antibiotic treatment of choice.

For some of us, bacterial resistance could mean more visits to the doctor, a lengthier illness, and possibly more toxic drugs. For others, it could mean death. The CDC estimates that each year, nearly 2 million people in the United States acquire an infection while in a hospital, resulting in 90,000 deaths. More than 70 percent of the bacteria that cause these infections are resistant to at least one of the antibiotics commonly used to treat them.

Antibiotic resistance, also known as antimicrobial resistance, is not a new phenomenon. Just a few years after the first antibiotic, penicillin, became widely used in the late 1940s, penicillin-resistant infections emerged that were caused by the bacterium Staphylococcus aureus (S. aureus). These "staph" infections range from urinary tract infections to bacterial pneumonia. Methicillin, one of the strongest in the arsenal of drugs to treat staph infections, is no longer effective against some strains of S. aureus. Vancomycin, which is the most lethal drug against these resistant pathogens, may be in danger of losing its effectiveness.

Although resistant bacteria have been around a long time, the scenario today is different from even just 10 years ago, says Stuart Levy, M.D., president of the Alliance for the Prudent Use of Antibiotics. "The number of bacteria resistant to many different antibiotics has increased, in many cases, tenfold or more. Even new drugs that have been approved are confronting resistance, fortunately in small amounts, but we have to be careful how they're used. If used for extended periods of time, they too risk becoming ineffective early on."

How Resistance Occurs

Bacteria, which are organisms so small that they are not visible to the naked eye, live all around us--in drinking water, food, soil, plants, animals, and in humans. Most bacteria do not harm us, and some are even useful because they can help us digest food. But many bacteria are capable of causing severe infections.

The ability of antibiotics to stop an infection depends on killing or halting the growth of harmful bacteria. But some bacteria resist the effects of drugs and multiply and spread.

Some bacteria have developed resistance to antibiotics naturally, long before the development of commercial antibiotics. After testing bacteria found in an arctic glacier and estimated to be over 2,000 years old, scientists found several of them to be resistant against some antibiotics, most likely indicating naturally occurring resistance.

If they are not naturally resistant, bacteria can become resistant to drugs in a number of ways (see graphic, left). They may develop resistance to certain drugs spontaneously through mutation. Mutations are changes that occur in the genetic material, or DNA, of the bacteria. These changes allow the bacteria to fight or inactivate the antibiotic.

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Bacteria also can acquire resistant genes through exchanging genes with other bacteria. "Think of it as bacterial sex," says David White, Ph.D., a microbiologist in the Food and Drug Administration's Center for Veterinary Medicine. "It's a simple form of mating that allows bacteria to transfer genetic material." The bacteria reproduce rapidly, allowing resistant traits to quickly spread to future generations of bacteria. …