For nearly half a century, farmers have been feeding poultry and some livestock the same antibiotics -- penicillin, tetracycline, bacitracin -- used to treat sick human beings.
The drugs aren't given just to animals that are ill, however. They are dispensed at routine intervals to healthy animals to help them grow bigger and faster with less feed and to become more profitable at slaughter.
This practice has come under attack from a growing number of scientists, public interest groups and medical organizations that contend it is helping to fuel new strains of bacteria in humans, strains that are growing more resistant to the drugs developed to vanquish them. Many of these "super-bugs" can infect people and cause fatal illnesses if antibiotics are no longer effective against them.
The campaign to stop the practice of giving antibiotics to healthy animals got a huge boost recently when one of the world's largest purchasers of meat and poultry joined the cause.
McDonald's Corp., which buys 2.5 billion pounds of poultry, beef and pork a year for its 30,000 restaurants worldwide, last month ordered its suppliers to eliminate by 2004 the use of antibiotics also given to humans, specifically when those drugs are used to make chickens, pigs and, less often, cattle grow faster.
"We saw lots of evidence that showed the declining rate of effectiveness of antibiotics in human medicine," said Bob Langert, McDonald's senior director of social responsibility. "We started to look at what we could do."
In effect, the marketplace has gone beyond what even the U.S. Food and Drug Administration tried unsuccessfully to accomplish in the 1970s -- eliminate the use of penicillin and tetracycline as growth promoters, an action that the U.S. Congress quashed.
Nevertheless, how much the policy will ease the resistance problem is a matter of debate.
"It's a tremendous step in reducing the pool of drug-resistant bacteria," said Dr. Stuart B. Levy, a professor at Tufts University School of Medicine in Boston and the author of "Antibiotic Paradox: How the Misuse of Antibiotics Destroys Their Curative Power."
Moreover, he says, it will encourage other companies to follow suit. A company with McDonald's clout "sets a standard for a large amount of other products we consume," said Levy, who founded the Alliance for the Prudent Use of Antibiotics, a nonprofit group that includes public health officials, veterinarians and doctors in 100 countries.
