Safe Food_ Bacteria, Biotechnology, and Bioterrorism - Marion Nestle [155]
Dealing with anthrax attacks, however, is no simple matter. As a preventive measure, officials treated 32,000 people who might have been exposed to anthrax with the protective antibiotic ciprofloxacin (cipro). Cipro is the most effective antibiotic against anthrax, largely because weapons programs deliberately created strains of the bacteria resistant to more common antibiotics such as penicillin. The drug produces unpleasant side effects—itching, swelling, and breathing problems—in nearly 20% of its takers. For this reason, and because of carelessness or inconvenience, many people stop taking the drug before completing the full course of treatment, thereby establishing conditions that favor the emergence of cipro-resistant anthrax—an utterly alarming scenario.31
Cipro has additional connections to food safety issues. It is a fluoroquinolone antibiotic closely related to another antibiotic, enrofloxacin, that is widely used to treat chickens and turkeys for respiratory ailments. The antibiotics are essentially the same; chickens metabolize enrofloxacin to cipro. Doctors have treated human infections with fluoroquinolone antibiotics since 1986, but resistance did not become a problem until 1996, when the FDA authorized use of these drugs to treat bacterial infections in poultry. As is customary, farmers fed the drug to entire flocks of chickens even if just a few were sick. Baytril, the enrofloxacin drug produced by Bayer, for example, is used on 128 million chickens worldwide and generates about $150 million in annual sales. By 1999, 18% of Campylobacter in chickens resisted enrofloxacin, and people exposed to such chicken bacteria could no longer be treated with cipro; 9,000 such cases were recorded that year. In 2000, the FDA proposed to ban the use of fluoroquinolone antibiotics in poultry feed. The other company making the poultry drug, Abbott Laboratories, agreed to discontinue using it in chickens, but Bayer contested the ban and keeps Baytril on the market. Bayer argues that the problem is overestimated and that withdrawing the drug would have little effect on the extent of antibiotic resistance. The company explains that using antibiotics in chickens is good for people as well as poultry: “If we are what we eat, we’re healthier if they’re healthier.”32 Drug companies may have little choice about giving up such drugs, however. Early in 2002, the three largest U.S. chicken producers, Tyson Foods among them, said they would reduce use of enrofloxacin, and McDonald’s said it had decided a year earlier not to use meat from animals treated with fluoroquinolone antibiotics.33
Anthrax is not yet resistant to cipro, but it is likely to become so if the drug is given indiscriminately to large numbers of people who do not need it and do not complete the full course of treatment. The continued use of the analogous drug in chickens will almost certainly increase the numbers and kinds of resistant bacteria. In Taiwan, 60% of pathogenic Salmonella isolated from hospital patients have been shown to resist cipro; genetic techniques indicated that the resistant bacteria originated in herds of pigs treated with the drug. Scientists have now shown that giving cipro to chickens rapidly selects for resistant Campylobacter.34
These antibiotics connect to the issues discussed in this book in one other way. In yet another ironic twist, Bayer, the maker of enrofloxacin, acquired Aventis CropScience in December 2001 for 6 billion (euros), thereby becoming the owner of StarLink corn and other transgenic varieties. The merger unites the crop protection activities of Bayer and Aventis into a new company, Bayer CropScience, expected to generate more than 8 billion in annual sales by 2005.35
THE NEW POLITICS OF FOOD SAFETY: BIOTERRORISM
In revealing the vulnerability of the United States to harm from terrorists,