Sadly, that trust could be short-lived. Cipro "may have the dubious distinction of being the antibiotic we destroy faster than any other," warns microbiologist Abigail A. Salyers at the University of Illinois. The problem is that bacteria are immensely adaptable critters. Expose them to antibiotics long enough, and they'll evolve ways to survive the drugs.
Infectious-disease experts stress that people exposed to anthrax, such as postal workers in affected mail centers, should take Cipro, at least until tests show either that they don't have the bug or that their bacterial strain is susceptible to other drugs. But those who gulp down Cipro merely out of fear are being dangerously irresponsible, putting both themselves and others at risk.
Why? The human body teems with bacteria. A broad-based antibiotic such as Cipro acts like a neutron bomb on this ecosystem, wiping out billions of microbes. Not only can that impair normal body functions in which bacteria play a role, such as digestion, but harmful germs can move in, like squatters taking over suddenly vacant houses.CRYING WOLF. Worse, antibiotics breed resistance. When you take a drug, the hardiest bacteria among constantly mutating strains survive, reproduce, and pass along defense mechanisms against drugs. Taking Cipro for weeks "is the perfect situation for the regular bacteria in the body to become resistant," says Dr. Carol J. Baker, a pediatrician at Baylor College of Medicine and president of the Infectious Diseases Society of America. Except in the case of an actual anthrax infection--rather than mere exposure--it's best to take the antibiotic for a few days only, to limit the development of resistance in the body's bacteria.
Even without resistance, these normally harmless bugs can turn nasty. Painful infections result when benign gut flora, such as E. coli, find their way to the urinary tract. Streptococcus bugs that live harmlessly in the throat cause pneumonia if they get into the lungs. Contract one of these diseases, and your doctor may prescribe Cipro. But if you've previously taken weeks of the antibiotic, your particular bug may already be primed to resist it. Not until you have to rush to the hospital will anyone know that something has gone horribly wrong. And the resistant microbes can spread to others.
Indeed, antibiotic resistance is one of the world's most pressing public-health problems. A single case of so-called multidrug-resistant tuberculosis costs more than $250,000 to cure--and the deadly germs are on the rise in many countries. Up to 30% of bacteria that cause ear infections and pneumonia in the U.S. can fight off standard antibiotics. The toll: thousands of hospitalizations and billions of dollars a year.
The quinolone drugs--of which Cipro is one example--were once part of the solution. They kill a wide spectrum of bugs, including strains resistant to other drugs. But resistance to quinolones has appeared in everything from meningitis-causing pneumococcus bugs to the E. coli in bladder infections.
It could get worse. Consider China, where quinolones have been widely overused for 10 years. The percentage of resistant E. coli, for one, has shot past 50%, rendering the whole class of drugs almost useless. "Unless we use Cipro wisely," says Dr. Stuart B. Levy of Tufts University, "we may lose one the most important drugs we have." By John Carey in Washington