The FDA took a small step towards preventing the growth of antibiotic-resistant bacteria last week when it announced a ban on certain uses of a class of drugs in food-producing animals. The ban on unapproved uses of these antibiotics in cattle, swine, chickens and turkeys will go into effect on April 5, 2012.

"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," Michael R. Taylor, FDA Deputy Commissioner of Foods, said in a press release.

The ban applies to certain drugs in the cephalosporin class of antibiotics, which are used to treat humans for diseases including pneumonia, urinary tract infections, pelvic inflammatory disease and skin and tissue infections. Overuse of antibiotics in food-producing animals can cause antibiotic-resistant bacteria to form making the drugs less effective in treating both animals and humans.

The ban's scope is limited to extra-label uses, treating an animal with a drug in a way not described on its label. Specifically, the ban prohibits using the drugs in species they are not approved for or at unapproved dose levels, frequencies, durations and routes of administration.

The order also prohibits the use of the drugs for disease prevention. It is unclear how much impact this aspect of the ban will have because cephalosporins are not used to prevent disease except in the case of surgeries, according to Dr. Dennis French, Section Head of the Department of Rural Animal Health Management at the University of Illinois at Urbana-Champaign.

French said extra-label use of antibiotics in animals is a common practice, although it is not always advisable.

"If you observe the withdrawal period before using the animal for food production, then it is safe. The animals have a broad spectrum of activity so extra label use can be effective," French said. "If you use higher doses than is on the label, you can have bacterial resistance problems in humans."

The limited ban is made narrower by a list of exceptions the FDA added to the order after a similar order was issued and revoked in 2008. The ban will not limit the use of cephapirin, a drug the FDA doesn't believe contributes significantly to antibiotic resistance. Veterinarians will still be able to prescribe cephalosporins for extra-label use in minor food-producing animals like ducks and rabbits. Additionally, veterinarians will still be able to prescribe drugs for diseases not indicated on the drug's label as long as they use the labeled dosage.

"The 2008 ban would have been really devastating because there are not a lot of antibiotics approved for use in pigs," said Liz Wagstrom, Chief Veterinarian for the National Pork Producers Council. "I think this is a pretty reasonable solution to address concerns about resistance while still allowing vets and farmers to work together to care for the animals."

It is unclear how much this ban will reduce the use of cephalosporins in food-producing animals because the FDA does not collect data about what portion cephalosporins sold and distributed are used for extra-label uses.

The FDA will enforce the ban by working with veterinarians and continuing to track the use of cephalosporins.

"We intend to focus our efforts on educating and working with veterinary groups such as AVMA about the new limitations," FDA representative Siobhan DeLancey said. "But clearly this will be looked at in connection with our compliance activities, i.e. tissue residue investigations and if there is evidence that the limitations were not complied with."

This ban comes less than eight months after a coalition of health and consumer organizations filed suit against the FDA for failing to meet its legal responsibility to address the rise of drug-resistant infections in humans linked to the overuse of antibiotics in animal feed. Antibiotics are mixed into feed at low doses to promote growth and prevent disease in unsanitary living conditions. The levels are too low to treat diseases so the surviving bacteria grow stronger and become resistant to antibiotics.

Cephalosporins are not used in feed and this ban does not address the practice of giving antibiotics to healthy farm animals, a system that accounts for 70 percent of all antibiotics used in the U.S., according to a Union of Concerned Scientists press release.