antimicrobials

Bayer Won't Pull Animal
Antibiotic Causing Drug
Resistance In Humans
By Sharon Lerner

Because the vast majority of the roughly 30,000 people who took Cipro in the anthrax scare were treating fear rather than exposure, the effectiveness of the bestselling drug was undermined even as its sales were skyrocketing. The more people who don't have bacterial infections take antibiotics, the less effective the drugs are when treating real problems, including TB, pneumonia, and bad colds.

Strangely enough, being partner to human overuse is not the only way Cipro-maker Bayer is at once reaping benefits from antibiotics and eroding their power. Bayer's drug Baytril--a super-antibiotic virtually identical to Cipro that is fed to more than 128 million chickens each year--is so clearly responsible for hundreds of Cipro-resistant infections in humans that the Food and Drug Administration has begun the process of withdrawing its approval.

Shortly after the FDA started its effort to ban potent, Cipro-like poultry pharmaceuticals last year, Abbott Laboratories voluntarily withdrew SaraFlox, Baytril's only competitor. Bayer instead appealed the agency's move, fighting to keep selling a drug that treats chicken respiratory infections--and pulls in an estimated $150 million worldwide each year. Cipro dominates the human antibiotic market, but Baytril is the market for chicken super-antibiotics. (In 1999 alone, 38,000 pounds of such super-antibiotics were fed to animals, according to the Animal Health Institute.) The FDA is expected to decide by the end of December whether to ban Baytril outright or to allow Bayer a hearing to defend it.

The agency bases its own case against Baytril on rising antibiotic resistance in human cases of food poisoning from a bacteria called campylobacter, which causes vomiting, diarrhea, and--in about 1 percent of cases--death. When such cases are extreme, Cipro is often the treatment of choice. Though people have had access to such powerful antibiotics since 1987, when Cipro was approved, resistance to them "did not increase among campylobacter organisms until 1996 and 1997, soon after the approval and use of these drugs in poultry," according to an FDA entry in the federal register.

When confronted with Baytril, bacteria in chicken experience a sort of quick, mini-evolution; while most die from the drugs, those with genetic differences that make them invulnerable go on to reproduce--and pass the mutations on. People can pick up these bacterial infections from eating undercooked chicken or juice from uncooked chicken.

When Baytril was approved in 1995, farmers began feeding it to entire flocks, even if only one bird was sick. Since then, the percentage of drug-resistant campylobacter infections in humans has shot up from about 1 percent to almost 20 percent, with more than 9000 Cipro-resistant cases reported in 1999 alone, according to a national database of food-borne infections.

While Baytril is used only on sick chickens and turkeys--and the other birds in their flocks--less powerful antibiotics are routinely also fed to healthy animals. Indeed, 70 percent of all antibiotics in this country are used to fatten up the profits by making commercially raised animals bigger, according to estimates by the Union of Concerned Scientists. Today, virtually all of the 8 billion chickens slaughtered each year are exposed to antibiotics at some point in their lives. (The roughly 36,000 antibiotic-free, certified-organic chickens provide the only exception.)

The dangers of the resulting antibiotic resistance are obvious. Take the case of Baytril: Most people with chicken-borne food poisoning won't require treatment, but for those who do, Cipro is less and less likely to work. As a result, experts say, the number of drug-resistant cases of campylobacter and salmonella, another chicken-borne bacteria, are shooting into the hundreds of thousands, while about 700 people now die each year from these bugs.

Even as the direct casualties are increasing, Tamar Barlam, a physician and infectious-disease specialist who directs the antibiotic-resistance project at the Washington-based Center for Science in the Public Interest calls them "just the tip of the iceberg." She worries about infections that may develop unnoticed as other bacteria--including some that aren't the intended target of the antibiotic--develop drug resistance.

An article in the October 4 New England Journal of Medicine points to just that sort of silent epidemic. The study traced drug-resistant, urinary tract infections in women to a single strain of E. coli the authors think was passed through infected meat. After finding the drug-resistant infection in California, the researchers looked for it in Minnesota and Michigan. "They found it in each of the states they investigated," says Barlam. "And I truly believe the more we look the more we're going to find."

Nevertheless, agricultural trade groups defend the widespread use of antibiotics in healthy chickens. "It improves the gut health of the bird and its conversion of feed, what we call the feed efficiency ratio," says Richard L. Lobb, spokesperson for the National Chicken Council. Without drugs, poultry producers say, chicken prices would go up. As for Baytril, Lobb argues that a connection between the drug and antibiotic-resistant infections in humans hasn't yet been proven. Lobb also supports the industrywide practice of putting Baytril in an entire flock's food and water, saying, "It's useless to try to treat a single bird."

Bayer did not comment, but its press release about Baytril states that the number of campylobacter infections attributed to eating chicken has been overestimated and that "there is no evidence that withdrawal of the product would . . . have a meaningful impact on resistant campylobacter infections in humans."

As Lobb sees it, antibiotics make chickens and turkeys healthier all around. "And if we are what we eat, we're healthier if they're healthier."

Many advocates are arguing just the opposite, of course, decrying the drugs that permeate the entire meat industry. In a recent study by the federal Center for Veterinary Medicine, researchers found that one in five packages of supermarket meat and poultry was infected with microbes, and 84 percent of the bugs were resistant to at least one antibiotic. Most were resistant to several.

The recent threats of bioterrorism have turned this wave of ever bolder microbes from a scientific curiosity into a real public health threat. Anthrax has yet to become resistant to Cipro, but other bacteria have been foiling antibiotics for decades. These drugs, which have vastly increased the safety of everything from surgery to childbirth, may no longer work the way we want them to. And in the wake of September 11, there are untold ways we really may need them.

The Centers for Disease Control and Prevention has renewed its focus on sloppy medicine--like using antibiotics, which kill bacteria, to treat viral infections--which it says accounts for fully one-third of the 150 million prescriptions written for antibiotics each year. And big, mainstream groups including the American Medical Association and the World Health Organization have joined in the call to stop the use of antibiotics in healthy farm animals.

If Baytril is forced off the market, the ban could mark the end of the shortsightedness that's made antibiotics a staple of chicken at the expense of people. "Why the hell aren't we giving a lot more careful thought to using critical human drugs in animals in the first place?" asks David Wallinga, a physician who directs the antibiotic-resistance project for the Institute for Agriculture and Trade Policy, an advocacy group based in Minneapolis. "We know that once these drugs lose their effectiveness, we're out of luck."