The End of Antibiotics?
SCIENTISTS AT THE U.S. CENTERS FOR Disease Control and Prevention are not sissies. They regularly handle bacteria and viruses that cause AIDS, smallpox, Ebola fever and other incurable diseases. There is one experiment, however, that they will not do: manipulate the DNA of garden-variety staphylococcus, the bacterium that lives on the skin and in the nose of half the population. Staph can cause blood poisoning. But the reason CDC researchers refuse to tinker with staph is that many strains of staph are not vulnerable to anything but one lone antibiotic. If an experiment produced a superstaph resistant to that last drug, and if the bug escaped, it could kill tens of thousands of people every month. Staph is not the only real-life Andromeda strain poised to strike. Last week, at the annual meeting of the American Association for the Advancement of Science in San Francisco, microbiologist Alexander Tomasz of Rockefeller University warned that many common bacteria are evolving resistance to more and more antibiotics. As a result, we are facing "nothing short of a medical disaster." he said.
It is not hard to see why. Before Alexander Fleming noticed in 1928 that a colony of mold in his lab dish exuded a substance that killed bacteria, infections such as blood poisoning, meningitis, pneumonia, tuberculosis and food poisoning killed millions of people every year. But with Fleming's penicillin and its descendants, medicine seemed to have true miracle drugs. It didn't last. Whenever a dose of penicillin killed a colony of, say, streptococcus, a few bugs that happened to be resistant to the drug survived. They reproduced by the trillions, bequeathing resistance to their progeny. They even passed the resistance genes to unrelated microbes, through bits of DNA called plasmids. Strep killed Muppeteer Jim Henson in 1990. Resistant infections killed 19,000 U.S. hospital patients (and contributed to the deaths of 58,000 more) in 1992. "Many of the diseases we thought we had under control are coming back," says the CDC's Mitchell Cohen.
That's because a host of common bugs now resist one or more antibiotics. Strains of pneumococcus, which can cause ear infections, meningitis, pneumonia and blood infections, became resistant to penicillin and to four other antibiotics in just the last six years. Some 20 percent of TB microbes resist isoniazid, the treatment of choice, and gonorrhea microbes resist penicillin. More than half the strains of Staphylococcus aureus, which causes blood poisoning, resist everything but vancomycin. And in a terrifying experiment, a British researcher recently showed that a microbe called enterococcus can transfer vancomycin resistance to staph. Staph and enterococcus meet on bandages, the scalp and hospital sheets every day. If staph picked up resistance to vancomycin, "we'd have a public-health nightmare," says Robert Gaynes of the CDC.
We got into this predicament through too much of a good thing. Doctors over-prescribe and patients overuse antibiotics, speeding up the process that kills wimpish bugs and leaves the resistant strains standing. Antibiotics in farm animals leave behind drug-resistant microbes in milk and meat; with every burger and shake, supermicrobes pour into your gut. There, they can transfer drug resistance to bacteria in the body, making you vulnerable to previously treatable infections.
How to conquer the superbugs is less obvious. "Half the pharmaceutical companies making antibiotics six years ago have left the field because they thought they had won the game," says Dr. Stuart Levy of Tufts University. One firm that has persevered is Schering-Plough, which is developing an antibiotic against enterococcus. But don't look for the new antibiotics before the millennium. A better hope may lie in vaccinations against bacterial scourges, but such shots are years away, too. Or, science might be able to figure out how bugs outfox antibiotics and construct new drugs that exploit the microbes' weaknesses. But "money from companies or the government for basic research into resistance is just not there," says Levy. The microbes that Fleming tamed are striking back.