Drug for chickens blamed for harder-to-treat food poisoning

Food poisoning is becoming harder to treat with drugs like Cipro because poultry producers are using a similar drug made by Bayer Corp. to treat chickens for respiratory disease, federal officials say.

Critics of Bayer's animal antibiotic Baytril argue that it is causing the development of Cipro-resistant strains of Campylobacter bacteria, the most common cause of foodborne disease. The U.S. Centers for Disease will report today that 19 percent of Campylobacter food poisonings last year were caused by Cipro-resistant bacteria, up
5 percent from 2000.

And an upcoming report by a University of Pennsylvania researcher indicates the rate of resistant infections reached 40 percent in the Philadelphia area last year.

The new figures add to a contentious debate about whether Bayer should be allowed to keep selling the antibiotic Baytril to treat respiratory infections in chickens.

Officials at the CDC and the Food and Drug Administration contend that Baytril is undercutting the effectiveness of Cipro, a close cousin of Baytril, in treating human cases of food poisoning. "It's really an incredible disaster," said Dr. Richard Michaels, a former chief of infectious disease at Children's Hospital and a member of Keep Antibiotics Working, a coalition of advocacy groups that is challenging the use of Baytril.

Physicians have tried to cut back on unnecessary use of antibiotics in human patients to slow the development of resistant bacterial strains. "But this problem in poultry is something physicians can't do much about," Michaels said. "Everybody eats chicken."

Bayer officials counter that the evidence is still shaky and maintain that critics are ignoring the benefits of Baytril. The company has appealed a proposal by the FDA two years ago to withdraw the agency's approval of Baytril for poultry use. "They didn't look at the risk of taking the product off the market," said Dennis Coleman, a veterinarian with Bayer's Agriculture Division in Kansas City. A coalition including the American Veterinary Medical Association and the American Farm Bureau Federation supports Bayer's position.

Other drugs available for poultry are less effective than Baytril, he said. The respiratory disease spreads rapidly, so producers are forced to either treat entire flocks with antibiotics or else destroy them. Many major producers, such as Tyson, ConAgra and Perdue, nevertheless have said they have stopped using or have limited their use of Baytril. Some fast food chains, such as McDonalds, Wendys and Subway, refuse to use Baytril-treated poultry.

The latest CDC figures, to be released today at a scientific meeting in Hilton Head, S.C., show 19 percent of U.S. cases of Campylobacter infections last year were resistant to Cipro, up from 13 percent in 1997 and 14 percent in 2000. The FDA approved Baytril in 1996.

Campylobacter is the leading cause of food poisoning, resulting each year in an estimated 2.4 million cases, 13,000 hospitalizations and
100 deaths.

But Bayer's Copeland said the rates reported by the CDC have fluctuated -jumping from 14 percent in 1998 to 18 percent in 1999, and back down to 14 percent in 2000. The national averages may be skewed by exceptionally high rates reported in certain states, notably Connecticut, he added.

It is possible that Baytril might lead to greater Campylobacter resistance to Cipro and other fluoroquinolone antibiotics, Copeland acknowledged. But the CDC figures aren't clearcut and travelers from countries where antibiotic-resistant bacteria are more common are another source of Cipro-resistant bugs, he said.

Frederick Angulo, the veterinarian who heads the CDC's National Antimicrobial Resistance Monitoring System, or NARMS, said the rates of Cipro resistance have indeed fluctuated. But the fact that Connecticut and several other states have high rates of Cipro resistance should be a matter of concern, he added, not an argument to ignore the figures.

"The more important question," Angulo continued, "is where is this resistance coming from?" Studies by the FDA and the CDC both point at use of fluoroquinolones in poultry. "Whether there's a big increase or a small increase in resistance is beside the point." If Baytril use is causing Campylobacter to develop a resistance to Cipro, then it is a threat to public health, he said.

NARMS has been monitoring antibiotic resistance only since 1997. But Irving Nachamkin, associate director of the Clinical Microbiology Laboratory at the Hospital of the University of Pennsylvania, has been monitoring Campylobacter for 20 years. As he will report in next month's issue of the CDC journal Emerging Infectious Diseases, no Cipro resistance was observed from 1982 to 1992. But in 1996, 8 percent of Campylobacter specimens in his lab were resistant to Cipro. The rate has gone up steadily -- 15 percent in 1997, 20 percent in 1998-99,
35 percent in 2000 and 40 percent in 2001.

Why the rate is so high in the Philadelphia area is unknown, Nachamkin said, but foreign travel doesn't seem to be the answer.

On the other hand, Bayer's Copeland said that the incidence rate of Campylobacter infections has declined by 41 percent since Baytril was introduced in 1996, even while per capita consumption of chicken increased. Baytril kills Campylobacter bacteria that otherwise would contribute to food-borne disease, he said.

"Our best estimate is a 25 percent reduction," Dr. Robert Tauxe, chief of the CDC's Foodborne and Diarrheal Diseases Branch, said yesterday. "I have no reason to attribute it to Baytril," he added, instead crediting improved processing of poultry carcasses, as well as greater care by consumers in handling and cooking poultry.

"I don't think there's any less Campylobacter on the farm," Tauxe added. Baytril is used to treat a respiratory infection, not Campylobacter, which doesn't make chickens sick. Bayer said less than 1 percent of chickens were treated with Baytril last year.

Representatives of the Keep Antibiotics Working coalition yesterday delivered 16,000 letters to Bayer that they said urged the company to abandon its appeal of the FDA's proposal to withdraw approval of Baytril.

Both the FDA and Bayer are to submit written testimony in the appeal to an administrative hearing judge next month and a hearing is scheduled to begin in April. The judge then makes a recommendation to the FDA commissioner.

By Byron Spice, Pittsburgh Post-Gazette Science Editor
Wednesday, November 20, 2002