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Antibiotics and the Chicken Connection

July 15, 2002|TRUDY LIEBERMAN | SPECIAL TO THE TIMES

Each year about 2.4 million Americans come down with infections caused by campylobacter, a bug transmitted through undercooked chicken or other foods contaminated with juices from raw poultry.

To treat the illness, doctors typically prescribe antibiotics called fluoroquinolones. These drugs are usually effective in knocking out the infection in a day or two, but if people are not treated, the illness can persist for up to three weeks.

A decade ago, about one in 100 people with campylobacter illness experienced antibiotic resistance; that is, the drugs didn't work against the bug. By 1999, remarkably, antibiotics failed to work in one of six people, according to the Food and Drug Administration. The FDA says that 80% of all chickens are now contaminated with campylobacter, and one in four of those chickens carries a drug-resistant form of the bacterium. How did this happen so fast?

In 1995 the FDA allowed poultry growers to use fluoroquinolones to prevent respiratory infections in chickens. The rationale went like this: If one chicken catches pneumonia, it quickly spreads to the rest of the flock. So if low doses of the drug were added to the birds' drinking water, it would prevent the rest of the flock from getting sick.

At the time, scientists from the federal Centers for Disease Control and Prevention argued that feeding fluoroquinolones to livestock would eventually make the drugs useless in treating campylobacter infections in humans.

Dr. David Satcher, then head of the CDC and later surgeon general, told the FDA that "the widespread use of fluoroquinolones in animals, even when limited to therapeutic use, will hasten the emergence of resistance, especially in bacteria transmitted by food."

The poultry industry argued that the antibiotics were used sparingly, on fewer than 1.5% of growers' flocks--still about 90 million chickens. The FDA agreed with the industry. Before long, however, the danger that Satcher warned about began to surface.

A study by the Minnesota Department of Health, published in the New England Journal of Medicine in 1999, found that 88% of the chickens purchased at grocery stores and other retail outlets were contaminated; 20% of them carried drug-resistant organisms. They also found that drug-resistant infections increased significantly in humans, from 0.8% in 1996 to 3% in 1998.

To be sure, antibiotic use in chickens and growing U.S. consumption of poultry are not the only factors contributing to antibiotic resistance in humans.

Doctors who prescribe antibiotics for patients with viral infections such as colds, for which antibiotics are ineffective, are part of the problem as well. So are parents who ask for antibiotics for their kids' ear infections when, in some cases, the drugs are not necessary.

Here's how chickens contribute to the problem: Like all animals, chickens carry many kinds of bacteria in their gut. Low doses of fluoroquinolones kill not only bacteria that cause pneumonia in chickens, but also some of the other germs, including campylobacter. Not all the campylobacter bugs are killed, however. Those that remain mutate and rapidly become resistant to the antibiotics.

During processing, when the birds are eviscerated and de-feathered, campylobacter can contaminate the birds' skin. Chickens are also chilled in a communal water bath where cross-contamination occurs.

When chicken is prepared for sale, juices accumulate in the package. If those juices drip on the cutting board in your kitchen or on uncooked foods such as fruits and vegetables, you can get sick from eating them.

Fortunately, something can be done before this problem gets worse. After a scientific link was found between drug resistance in humans and fluoroquinolones fed to chickens, the FDA in 2000 withdrew approval of two drugs used to treat sick chickens: sarafloxacin (SaraFlox), made by Abbott Laboratories, and enrofloxacin (Baytril), made by Bayer.

"We don't believe that fluoroquinolones are safe to use in poultry," says Dr. Linda Tollefson, deputy director of the FDA's center for veterinary medicine. "Chickens treated with fluoroquinolones are not safe to eat."

Abbott agreed to remove sarafloxacin from the market, but Bayer is challenging the FDA action.

"We can't find the link between the use of Baytril and poultry," says Bayer spokesman Bob Walker. "We strongly believe in the product. Instead of being a detriment, it's a benefit to safe food."

Walker also contends that no other drug works on chickens with respiratory illness. But the FDA says there are other antibiotics that can be used.

The fight against fluoroquinolones has found some unexpected support from industry. The Wendy's restaurant chain, which uses 200 million pounds of poultry a year, doesn't buy birds that have been treated with fluoroquinolones. Neither does McDonald's. And Foster Farms, the largest poultry producer on the West Coast, says it does not use fluoroquinolones to treat its flocks.

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