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FDA Planning To Halt Ag Use of Two Antibiotics

Officials in the Food and Drug Administration (FDA) announced plans to ban two antibiotics in the fluoroquinolone family that are used by poultry farmers to treat respiratory problems in chickens and turkeys. Agency officials say this use of the drugs increases the likelihood that humans will become infected with fluoroquinolone-resistant strains of campylobacter, the nation's most common bacterial foodborne illness. The proposed ban, which would be the first by the agency involving an antibiotic to which bacteria have grown resistant, is a response to a growing problem that has produced increasing concern among microbiologists and the broader public health community.

The two fluoroquinolones in question—sarafloxacin, made by Abbott Laboratories of North Chicago, Ill., and enrofloxacin, manufactured by Bayer Corp.'s animal division, of Shawnee Mission, Kans.—are not approved for use in humans. However, others within that drug family are considered to be of vital importance for treating a broad range of clinical infections. FDA's concern is that "once you have resistance" in any members of that class "it confers cross-resistance" to all members within the class, says Stephen Sundlof, director of the FDA Center for Veterinary Medicine. "Indications are that we are starting to see a substantial number of people adversely affected. They are being treated with a drug that is not effective in managing the disease."

Several years ago, agency officials proposed—but still have not fully implemented—an elaborate risk assessment system for evaluating antibiotics being considered for agricultural uses. Nonetheless, the proposed action would be the first specifically aimed at reducing the use of antibiotics in agriculture, a practice frequently criticized as contributing to the overall level of antibiotic resistance among pathogens and also raising the risk of animal-to-human transmission of resistant organisms. The two fluoroquinolones in question were approved for use in poultry in the mid-1990s, and since then the incidence of resistance to fluoroquinolones in pathogens infecting humans has markedly increased. "We will be monitoring impact, and we are hoping the resistance will go down," Sundlof says. "There will be less selective pressure on the campylobacter bacterial population with the removal of this drug in chickens."

Chickens are the primary food source for the spread of campylobacter, which causes nearly 2 million cases of foodborne disease in the United States annually, according to Sundlof. Of those, between 146,000 to 190,000 "are of the resistant type," he says. Prior to 1996, resistant cases in humans "[were] very low, 1% or less." FDA officials have been monitoring campylobacter in poultry and human populations in recent years. About 10% of the infections among chickens are resistant; in humans, resistant cases have risen from 13.3% in 1998 to 17.6% in 1999. Agency officials estimate that the health of 5,000 Americans is compromised by use of drugs for treating infections in farm animals.

Abbott said it would withdraw its antibiotic immediately, and is being allowed "until the end of April to deplete its stock," Sundlof says. But Bayer officials say they might ask the FDA to reevaluate the proposed ban, arguing that the company needs more time to evaluate FDA data. The company was told it could have an additional 30 days to develop a factual basis for its case against the ban. Should company officials present additional arguments to the agency, there will be an additional period of evaluation. "How much information they provide will dictate the time it will take us to review," Sundlof says. If Bayer challenges the action, "then you're talking about a very protracted process, possibly years," he says.

Public health officials at other organizations, including the federal Centers for Disease Control and Prevention in Atlanta, Ga., and the World Health Organization, support this ban and would like it to be broadened. Moreover, others are saluting the FDA move. For example, Michael Jacobson, executive director of the Center for Science in the Public Interest, applauds the agency for proposing to reverse "its ill-considered" approval of fluoroquinolones for poultry flocks. "That use has greatly increased the prevalence of fluoroquinolone-resistant foodborne pathogens," he says. "A ban should significantly improve the effectiveness of fluoroquinolones in treating patients. Ideally, the FDA will go farther in the future by banning the use of medically useful antibiotics to fatten livestock."

However, many experts within the agricultural and pharmaceutical communities oppose removing these products from use in agricultural settings. Moreover, several members of Congress, concerned about the economic impact of the ban on farmers and on the drug industry, wrote to Health and Human Services Secretary Donna E. Shalala after the ban was announced, expressing their reservations. "The FDA's decision regarding fluoroquinolone use will set a precedent for all future activity regarding antibiotic resistance and will have a significant impact on the livelihood of hard-working poultry growers and on food safety," asserts Representative Calvin M. Dooley (D-Calif.). "Given these implications, FDA must make the process more transparent and must render a decision based on fact rather than fear."

Marlene Cimons
Marlene Cimons is a Washington reporter for the Los Angeles Times covering health policy.