Can Antibiotic-Resistant Bacteria Skip Over The Farm Fence?

The findings of a new study certainly make it look that way.

Workers at farms that use antibiotics tested positive for drug-resistant bacteria associated with pigs. (Photo: Lynn Graesing/Getty Images)

Jul 10, 2013· 2 MIN READ
Clare Leschin-Hoar's stories on seafood and food politics have appeared in Scientific American, Eating Well and elsewhere.

Folks sounding alarm bells over the continued widespread use of antibiotics in industrial animal production recently got some scientific backup to support their case. Ironically, it may have been missed by those of you chowing down on hotdogs and BBQ chicken this past Fourth of July.

A group of scientists swabbed the noses of two distinct groups of North Carolina hog farm workers looking for antibiotic-resistant Staphylococcus aureus. One group worked in a conventional industrial hog farm; the other in an antibiotic-free operation. What’d they find? According to the new study, just over 40 percent of both groups carried staph bacteria—but several of those who worked in the conventional industrial pig farm also carried something called ST398, also known as pig MRSA.

What’s the difference between the bacteria, and why does it matter?

Maryn McKenna, author of SuperBug, covers the new study for Wired, writing, “The question of whether livestock production’s use of antibiotics causes antibiotic-resistant bacteria to move into the wider world is much argued-over, and pig MRSA, or ST398 to be polite, is crucial to that dispute. That’s because, unlike most resistant bacteria, it has a genetic signature that makes an inarguable link back to farm drug use.”

Gail Hansen, senior officer for Pew Charitable Trusts campaign on human health and industrial farming, says that we can find Staph bacteria on the general population, but the fingerprint of the ST398 brings it straight back to agriculture.

“We’re seeing that this livestock-associated strain of Staphylococcus aureus is multi-drug-resistant and can go from person-to-person. It can leave the farm, and if it leaves the farm, it goes everywhere. It doesn’t stop because you live in the city or just because you don’t eat meat,” she tells TakePart.

Chris Heany, one of the study’s authors and assistant professor of environmental health sciences and epidemiology at Johns Hopkins Bloomberg School of Public Health, says when they looked at Staphylococcus aureus, the livestock-associated strains were only present in the industrial hog operation, not the antibiotic-free environment.

“That’s the key thing. What’s remarkable is while everyone in the study had direct or indirect contact with livestock, we only observed drug-resistant [bacteria] with multiple genetic characteristics in the industrial group. That’s interesting, and builds on the work being done by Tara Smith at the University of Iowa,” Heany tells us.

According to The New York Times Mark Bittman, Smith’s work showed evidence that MRSA was indeed moving from pigs to humans in Iowa and Illinois. And, like North Carolina, Iowa and Illinois are among the top large-scale pork-producing states.

Worry of antibiotic use in animal production isn’t new. As we told you back in February, even the U.S. Food and Drug Administration is growing concerned about antibiotic resistance stemming from livestock production. In 2011, 30 million pounds of antibiotics were sold for use in beef, pork and poultry production. Thats four times the amount sold to humans who were sick—a stunning statistic, especially given our antibiotic arsenal that keeps us humans healthy is relatively small to begin with.

Will a study like this move the U.S. meat industry away from regular antibiotic use? Probably not in the immediate future, but it adds particularly compelling information to this very important conversation.