ROCKVILLE, Md. (Cox News Service) - Escalating rates of antibiotic-resistant human diseases demand a sweeping re-examination of the ways that such drugs are now used on the nation's farms, the Food and Drug Administration warned Monday.

In proposing new regulations that could, for the first time, suspend farmers' use of any antibiotics found to promote the spread of resistant human pathogens, the agency said the link between farm use of such drugs and some human diseases is now indisputable.

Although the spread of resistant microbes from the farm to human populations has been documented in only a few of the 106 antibiotics used in animals, FDA officials said the risks are serious enough that the agency's role in assuring "an abundant and affordable supply of meat, milk and eggs" will have to take a back seat to human health concerns.

"FDA's primary goal must be to protect the public health by preserving the long-term effectiveness of antimicrobial drugs for treating diseases of humans," said Stephen Sundlof, director of the agency's Center for Veterinary Medicine, at a three-day public hearing on the proposal in Rockville, Md.

Under the new rules proposed by the FDA, the agency would create a regulatory framework that would set specific thresholds at which the appearance of resistance would trigger an automatic halt to agricultural uses of any drugs. The regulations would apply to new drugs developed for agricultural use after the laws go into effect and could also apply to drugs already in use.

The new rules aired Monday could require congressional approval and will take at least a year to be enacted, officials said.

New information from the federal Centers for Disease Control and Prevention in Atlanta shows, for the third year in a row, elevated levels of resistant strains of the country's two leading bacterial causes of foodborne illness: Campylobacter and Salmonella.

Although health officials can't be sure how much of the increase in resistant gastrointestinal illness is due to the farm - and how much is due to heavy prescribing of the drugs by doctors - they say farm use is contributing significantly to the problem.

Estimates of total farm use of antibiotics range from one-third to two-thirds of all antibiotics used in the United States.

"With sufficient exposure to antibiotics, wherever it is, resistance will rise," said Glenn Morris, a former CDC epidemiologist and chairman of the University of Maryland School of Medicine. "It is not a matter of if. It is a matter of when."

Farmers and livestock professionals say they need to combat resistant disease also. "There are a lot of thing we can do to reduce our reliance on antibiotics, but for some diseases these drugs are our ultimate gun, too," said Dennis Wages of North Carolina State University.

In a separate action, the FDA is moving to revoke the use of quinolone antibiotics by the poultry industry, which the agency blames for a sharp increase in resistance among Campylobacter microbes, which cause an estimated 2.4 million cases a year of what is commonly called "food poisoning."

Banning an antibiotic already in use, however, is a long, contentious process. The quinolone ban is currently being challenged by the poultry industry and the pharmaceutical company that manufactures the drug they use.

Public health advocates said swift action is warranted. "The first concern has to be human health," said Richard Wood, executive director of the Food Animal Health Concerns Trust, a Chicago-based food policy group. "When you're trying to save an important antibiotic, due process that takes years to accomplish is unacceptable."

The new rules would be especially restrictive for several classes of antibiotics that are considered drugs of last resort for some human infections - a class that includes the quinolones, vancomycin and certain cephalosporins.

Although most resistant infections are thought to be attributable more to overuse by doctors and hospitals - not to agriculture - Morris said the need to reserve the newest drugs for human use is urgent.

"We are fighting for time, and when you transfer resistance from the farm to human populations, you accelerate the process," he said. "New drugs have a limited life span, and that window is closing."

Copyright 2001 Cox News Service. All rights reserved.