WASHINGTON — Federal drug regulators announced on Wednesday that farmers and ranchers must restrict their use of a critical class of antibiotics in cattle, pigs, chickens and turkeys because such practices may have contributed to the growing threat in people of bacterial infections that are resistant to treatment.
The medicines are known as cephalosporins and include brands like Cefzil and Keflex. They are among the most common antibiotics prescribed to treat pneumonia, strep throat, and skin and urinary tract infections. Surgeons also often use them before surgery, and they are particularly popular among pediatricians.
The drugs’ use in agriculture has, according to many microbiologists, led to the development of bacteria that are resistant to their effects, a development that many doctors say has cost thousands of lives.
Antibiotics were the wonder drugs of the 20th century, and their initial uses in both humans and animals were indiscriminate. Farmers became so enamored of the miraculous effects of penicillin and tetracycline on the robustness of cattle, chickens and pigs that the drugs were added in bulk to feed and water, with no need forprescriptions or any sign of sickness in the animals.
By the 1970s, public health officials had become worried that overuse was leading to the birth of killer infections resistant to treatment. Since then, the Food and Drug Administration has undertaken fitful efforts to wean farmers, ranchers and veterinarians from excessive use of the medicines, but the vast majority of antibiotics used in the United States still go to treat animals, not humans. Meanwhile, outbreaks of illnesses from antibiotic-resistant bacteria have grown in number and severity.
A decade ago, the F.D.A. banned indiscriminate agricultural uses of a powerful class of antibiotics, called fluoroquinolones, that includes the medicine Cipro. Wednesday’s announcement was another of the F.D.A.’s incremental steps.
“We believe this is an imperative step in preserving the effectiveness of this class of important antimicrobials that takes into account the need to protect the health of both humans and animals,” said Michael R. Taylor, deputy commissioner for foods at the agency.
Cephalosporins are not used as widely in livestock as penicillin, since they require a prescription from veterinarians. But the drugs are routinely injected into broiler eggs and used in large doses to treat infections in cattle and other animals.
The new rule will restrict only some of these uses and is therefore a modest step that, while applauded by consumer advocates, led many to call for far tougher measures.
“This is particularly important because cephalosporins are so important to human health, but it’s only a first step,” said Laura Rogers of the Pew Charitable Trusts, which has advocated restricting agricultural uses of antibiotics.
The F.D.A. initially proposed cephalosporin restrictions in 2008 but withdrew the rule before it could take effect because of opposition from veterinarians, farmers and drug companies. The rule announced Wednesday is less strict than that one, since it still allows veterinarians to use the drugs in to treat sick animals in some ways the F.D.A. has not specifically approved, and wide discretion to treat small-scale-production animals like ducks and rabbits. The rule bans routine injections of cephalosporins into chicken eggs and large and lengthy dosing in cattle and swine.
Dr. Christine Hoang, assistant director of scientific activities at the American Veterinary Medical Association, said the new rule was a vast improvement over the one proposed in 2008.
“We thought the original order was too broad and unnecessarily prohibited uses that were not likely to cause problems for human health,” Dr. Hoang said.
Dr. Scott A. Brown of Pfizer, which makes cephalosporins used in animals, said the company “acknowledges the intent of the proposed order to respect veterinary discretion in determining the appropriate and responsible use of cephalosporin antibiotic medicines in the interest of animal health and human health.”
The F.D.A. has yet to make final a guideline proposed in 2010 that would edge the agency closer to banning uses of penicillin and tetracycline in feed and water for the sole purpose of promoting the growth of animals or preventing illness that results from unsanitary living conditions. This issue has generated intense controversy among farmers and ranchers who contend that public health officials have exaggerated the danger of agricultural uses of antibiotics to humans.
When asked about the penicillin guideline, Mr. Taylor of the F.D.A. said, “We’re hopeful that in the coming months, we’ll be able to carry forward on that work.”
Representative Louise M. Slaughter, a Democrat from New York and a microbiologist, said the F.D.A. had been too slow and too timid. “We are staring at a massive public health threat in the rise of antibiotic-resistant superbugs,” she said. “We need to start acting with the swiftness and decisiveness this problem deserves.”
But Dr. Gatz Riddell, executive vice president of the American Association of Bovine Practitioners, a veterinarian group, said the dangers of agricultural uses of antibiotics had been greatly exaggerated. “It is highly misunderstood in the human-health community how much antibiotics are used in animals who are not sick or at risk of becoming sick,” he said.
