It's the sort of thing any good poultry farmer notices right away: a few of the birds in a so-called grow-out building have started snickering--the chicken equivalent of coughing. A respiratory infection, if that's what they have, could spread to the 20,000 other birds in the chicken house in a matter of days. The vet recommends the antibiotic enrofloxacin--the animal version of Cipro. Since it's not practical to treat the birds individually, the farmer pours a 5-gal. jug of the drug into the flock's drinking water. Five days later the birds are doing fine. Disaster has been averted.
Or has it? While enrofloxacin kills the type of bacteria that sickened the chickens, it doesn't quite eliminate a different strain, called Campylobacter, that lives in the intestine. The surviving germs, which don't cause any poultry diseases, quickly multiply and spread the genes that helped them fend off the antibiotic. Six weeks later, when the broilers are carved up at the slaughterhouse, resistant bacteria spill out everywhere. Even with the best sanitary controls, some campylobacter is shrink-wrapped along with the thighs, breasts and drumsticks that are delivered to your kitchen counter.
That's where the real trouble begins. Campylobacter is a major cause of food poisoning in humans. Less than diligent hand washing or improperly cooked meat could park you on the toilet for the next few days. And if you're sick enough to need medical treatment, you might be out of luck. Chicken Cipro is so closely related to human Cipro that any germ that has become resistant to the animal drug can shrug off the human one just as easily. Before 1996, when enrofloxacin was approved in the U.S. for use in poultry, the number of Campylobacter infections in people that were resistant to Cipro and its chemical cousins was negligible. By 1999, it had jumped to 18%--a clear sign, many researchers argue, that at least part of the increase is directly tied to the use of antibiotics on poultry farms.
Welcome to the harrowing world of antibiotic resistance, where drugs that once conquered everything from pneumonia to tuberculosis are rapidly losing their punch. Chicken Cipro is only the latest example of how humans are burning their pharmacological bridges. Feed-lot operators are dosing their livestock with antibiotics to keep them healthy under stressful growing conditions. Parents are demanding the most powerful broad-spectrum agents--often by brand name--for their children's upper-respiratory infections. Consumers are snapping up cutting boards, dishwashing soap and baby toys laced with antibacterial compounds, hoping to make their homes perfectly sterile and safe.
Doctors have long understood that the indiscriminate use of antibiotics usually backfires, selecting for germs that are tough to kill. But no one was prepared for how easily resistance could spread even when the drugs were used in what was thought of as appropriate treatment.