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FDA waffles as superbugs spread
The FDA is sending mixed signals: It unveiled new limits this week on one class of livestock antibiotics, two weeks after scrapping a 34-year push to limit two others. All three can promote drug-resistant bacteria, aka superbugs.
BUGS ON DRUGS: Industrial hog farms attract lots of bacteria, and low-dose antibiotics in livestock feed can help them develop resistance to human medicine. (Photo: Patrick Pleul/ZUMA Press)
If you didn't keep up with the Federal Register over the holidays, you're not alone. The official daily journal of U.S. government can be drier and less digestible than any leftover turkey or fruitcake.
But it often seems to save its more scandalous news for holidays and weekends. Last month, for example, this bulletin quietly appeared before Christmas: The Food and Drug Administration is canceling a 34-year attempt to limit two antibiotics in livestock feed, despite a trough of research linking them to the rise of drug-resistant bacteria, or "superbugs."
The FDA revealed its decision on Dec. 22 with little fanfare, but still braced for a backlash. In its official notice, the agency said it "remains concerned about the issue of antimicrobial resistance," but will now focus on "the potential for voluntary reform."
"Today's action should not be interpreted as a sign that FDA no longer has safety concerns," the notice states, "or that FDA will not consider re-proposing withdrawal proceedings in the future, if necessary."
And this week, as if to prove its superbug-fighting cred, the FDA made a very different (and more publicized) move: It unveiled new restrictions for a class of antibiotics called cephalosporins, which are often injected into healthy animals but not added to feed. In a press release Wednesday, FDA Deputy Commissioner Michael Taylor called this "an imperative step in preserving the effectiveness of this class of important antimicrobials," citing a need to protect both humans and animals.
The Dec. 22 and Jan. 4 notices were just two weeks apart, but they seem to come from different dimensions. First the FDA dropped a three-decade push to regulate two kinds of livestock antibiotics, then it launched a new plan to start regulating a third, boasting that it's taking initiative against antibiotic resistance. With microbes quickly growing immune to a variety of drugs, this give-and-take can appear contradictory.
The FDA's Center for Veterinary Medicine did not respond to MNN's requests for comment, but the agency has long voiced concern about drug resistance. The Dec. 22 decision could be a result of pressure from industry or Congress — both have long fought efforts to regulate livestock drugs — or part of a strategy to pick and choose political battles. Whatever the case, scientists and public-health advocates are cheering the Jan. 4 decision, expressing relief the FDA is doing anything.
"It's good that we're finally having this action," physician David Wallinga of the Institute for Agriculture and Trade Policy tells Reuters. "But literally thousands of people have been affected by these cephalosporin-resistant infections in the meantime."
Antibiotic-resistant Staphylococcus aureus, magnified 50,000 times. (Photo: CDC/Matthew J. Arduino)
The FDA got itself into this mess in the 1950s, when it first approved two classes of antibiotics — penicillin and tetracycline — as feed additives. The idea was to prevent infections and boost growth in healthy animals by giving them small, "subtherapeutic" doses on a regular basis.
But the drugs had a dark side. While low-dose antibiotics can have short-term benefits, they kill weak microbes and leave hardier ones behind. Those survivors go on to repopulate the colony with stronger genes, breeding increasingly drug-resistant bacteria. In 1969, the U.K. government's "Swann Report" suggested that rising rates of resistant microbes had evolved on industrial livestock farms.
The FDA assigned a task force to study the issue in 1970, and three years later proposed banning antibiotic-laced feed unless the industry could prove it was safe. Meanwhile, a major study in 1976 seemed to prove the opposite: Researchers from Tufts University set up a poultry farm, gave the chickens antibiotic-laced feed, watched as drug-resistant bacteria spread from chicken to chicken, and then watched them spread to people. The FDA issued a "Notice of Opportunity for a Hearing" in 1977 to ban penicillin in animal feeds, followed months later by another to ban tetracycline.
Those hearings never took place, largely due to Congress rebuffing the FDA and demanding further research. (The FDA did commission more studies at lawmakers' requests, but proof of subtherapeutic drugs' safety remained elusive.) Through it all, the FDA's 1977 proposals stood defiantly for 34 years — until last month, when it finally withdrew them.
S. aureus bacteria escaping destruction by human white blood cells. (Photo: NIAID/RML)
The case against pre-emptive antibiotics has grown over the years, collecting support from major science and health groups such as the National Academy of Sciences, the American Medical Association and the World Health Organization. And the fact that drug-resistant bacteria can infect humans as well as animals — as seen in the recent growth of MRSA, or methicillin-resistant Staphylococcus aureus — has added urgency.
Despite the potential benefits of the new ruling on cephalosporin drugs, it's worth noting that cephalosporins represent a minor class of livestock antibiotics. According to a 2010 FDA report, they're one of the least-used animal antimicrobials in terms of net weight. Only 24,588 kilograms of cephalosporins (54,207 pounds) were used on U.S. livestock in 2010, compared with 870,948 kg of penicillins (1.9 million pounds) and 5.6 million kg of tetracyclines (12.3 million pounds).
Critics also point out the FDA's cephalosporin crackdown isn't comprehensive. It only applies to some extralabel uses of certain cephalosporins in healthy cattle, swine and poultry, partly so vets can still use the drugs to treat genuinely sick animals. But it also offers exceptions for "extralabel use of approved cephapirin products in food-producing animals," as well as extralabel use in "food-producing minor species," such as ducks or rabbits. That's weaker than an earlier FDA proposal from 2008.
Still, as the FDA's Jan. 4 press release noted, cephalosporins aren't exactly chopped liver — the drugs are commonly used in humans to treat pneumonia, strep throat, skin and soft-tissue infections, pelvic inflammatory disease, diabetic foot infections and urinary tract infections. "If cephalosporins are not effective in treating these diseases," the release warns, "doctors may have to use drugs that are not as effective or that have greater side effects."
See the video and links below for more about superbugs and their war on our drugs:
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