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The problem is that bacteria share genetic information much more readily than anyone thought. Individual cells--often from different species--routinely exchange tiny loops of DNA called plasmids. They will even pick up snippets of DNA from dead bacteria or viruses. Once a strain of bacteria survives destruction by antibiotics, chances are it will eventually pass on the genes for resistance to other germs. "It's a numbers game," says Dr. Stuart Levy, a Tufts researcher and author of The Antibiotic Paradox. And because they live everywhere and reproduce quickly, bacteria have the upper hand.
It doesn't help matters that many Americans have come to think of antibiotics as tools for prevention. Patients will often ask for the drugs to keep their colds from turning into sinus infections, even though antibiotics have no effect on the viruses that cause colds in the first place.
What's harder to evaluate is the treatment of something like a middle-ear infection, which is indeed caused by several different types of bacteria, including Pneumococcus. Left alone, a handful of these infections could lead to permanent hearing loss. And yet their treatment has, in just the past 10 years in the U.S., boosted the prevalence of penicillin-resistant pneumococci to more than 20%.
No one yet advocates allowing all bacterial infections to run their course. But don't be surprised if your doctor takes more of a wait-and-see approach with your next case of flu (which, like a cold, is caused by viruses). Hospitals are also learning how to vary the drugs they give their patients to diminish the chances of selecting for ever more resistant germs.
Relief may soon be on the way. Thanks to advances in the new science of genomics, researchers have started to scour bacterial DNA for new and possibly better targets for drug development. The goal is to produce a compound that works so differently from today's antibiotics that germs won't know how to start developing resistance. Other research has produced drugs that help restore penicillin's ability to clobber resistant germs, provided the compounds are given in combination.
In the meantime, the FDA is so concerned about the possibility of losing Cipro and similar drugs that it has asked pharmaceutical companies to stop selling them to poultry farmers. Bayer, which manufactures both Cipro and enrofloxacin, is contesting the idea, arguing that resistance levels have stabilized and can be managed.
The question remains: How much resistance are you willing to live with? "Most infections you get that are drug resistant came to you drug resistant," Levy says. You can do your part to halt their spread by not taking antibiotics unnecessarily and following a doctor's orders when they are prescribed. Saving pills for later, so you don't have to get a new prescription, is definitely a bad idea. "We'll be in this business for a long time to come," says Dr. Stephen Lory, professor of microbiology and molecular genetics at Harvard Medical School. "We will come up with something; bacteria will become resistant. We'll come up with something new." It's the kind of contest where no matter how hard you fight, the best you can hope for is a draw.
--Reported by David Bjerklie and Alice Park/New York