Finally, a smoking gun connecting livestock antibiotics and superbugs
How does the livestock industry talk about antibiotics? Well, it depends on who’s doing the talking, but they all say some version of the same thing. Take the National Cattlemen’s Beef Association; they say there is “no conclusive scientific evidence indicating the judicious use of antibiotics in cattle herds leads to antimicrobial resistance in humans [MRSA].”
… You have to look at specific bug/drug combinations and figure out what are the potential pathways for antibiotic-resistant material to transfer from animals to humans. Studies have been done, and have come to the conclusion that there is a vanishingly small level of risk.
The message is clear. Until scientists trace a particular bug from animals to humans and show precisely how it achieved resistance and moved from farm to consumer, there’s no smoking gun. Thus industry leaders’ heads can remain firmly buried in the sand.
A study in the journal mBio, published by the American Society for Microbiology, shows how an antibiotic-susceptible staph germ passed from humans into pigs, where it became resistant to the antibiotics tetracycline and methicillin. And then the antibiotic-resistant staph learned to jump back into humans.
“It’s like watching the birth of a superbug,” says Lance Price of the Translational Genomics Research Institute, or TGen, in Flagstaff, Ariz.
The superbug at issue is a strain known as “pig MRSA,” or ST398. It’s the bug I discussed with WIRED writer and Scientific American editor Maryn McKenna recently, and the same one scientists found on retail meat in another study.
The mBio study authors found that ST398 started as a not-quite-resistant strain of staph in humans, jumped to pigs, where it acquired resistance to antibiotics, jumped back to the humans who lived near the pigs, caused disease, and then, like many rural residents before it, left the farm to find its fortune in the big city.
McKenna on her Superbug blog on WIRED warns those who might consider all this “no big deal” and sums up the significance of the new study’s findings:
The important development in the story of ST398 is its move back off the farm into humans, causing first asymptomatic carriage in that original family, and then illnesses in other Dutch residents, and then outbreaks in healthcare settings, and then movement across oceans, and then appearance in retail meat, and then infections in people who had no connection whatsoever to farming — all from an organism with a distinctive agricultural signature.
This pathway is exactly the one described by critics of the overuse of antibiotics by industrial agriculture. Big Ag’s response to date has been to say, “Prove it!”
Scientists now have. So what happens next? Well, don’t expect Big Ag to capitulate. In fact, when I spoke with Paul Sundberg, the vice president of science and technology for the National Pork Board, he disputed Maryn’s assessment of this study.
While stressing he had not yet fully reviewed the paper, Sundberg called it “an interesting finding with no human health implications.” He believes the study simply used advanced techniques to confirm what we already know — that staph moves from people to animals. He also downplayed the overall threat from pig MRSA generally, putting it behind hospital- and community-acquired infections as a cause for concern.
To Sundberg, antibiotic resistance is a natural process that is a consequence of using antibiotics — period. In other words, a cost of doing business.
Given the influence groups like Sundberg’s wield at USDA and FDA, don’t expect regulators to do anything either. The FDA just announced that it will trust companies to voluntarily control agricultural antibiotics, and this study is unlikely to change their minds.
There’s a bill in Congress that would provide some regulation — it’s the Preservation of Antibiotics for Medical Treatment Act of 2011 (PAMTA) authored by Rep. Louise Slaughter (D-N.Y.), Congress’ only microbiologist. We can only hope that after they see this science, they’ll finally pass it.
Of course, the House is currently controlled by Republicans, who seem at the moment to be far more interested in expanding the government’s access to women’s reproductive parts than, well, most everything else. So until their priorities change, or the legislators themselves are voted out, we may just have to learn to love our new born-on-the-factory-farm, incurable superbugs.
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