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Environmental Health

Factory Farm Workers More Likely to Carry Drug-Resistant Staph

New research from UNC-Chapel Hill finds disturbing trends in what kinds of farm workers carry more virulent strains of bacteria.

By Stephanie Soucheray

Eliza MacLean runs Cane Creek Farm south of Burlington, where for 10 years she and her family have been raising between 150 and 300 pasture-grazed pigs on their 45-plus-acre farm.

And when researchers from UNC-Chapel Hill asked if they could swab her and her children’s noses for a study, MacLean responded enthusiastically.

“I said ‘Hell, yeah!,’” remembers MacLean.

Eliza McLean and friend. Photo courtesy Cane Creek Farm.

Eliza MacLean and friend. Photo courtesy Cane Creek Farm

Those UNC public health researchers were looking to see if there might be a link between different types of farming practices and resistance to antibiotics. In particular, they were looking to see what kinds of farm workers might be carriers of antibiotic-resistant Staphylococcus aureus, at times famous for risking the lives of hospital-bound patients as well as people in the community.

MacLean said it came as no surprise when the researchers told her neither she, her children nor her four employees were carrying the antibiotic-resistant bacteria in their nasal passages, where it commonly lurks.

Workers and bacteria

Last month, the UNC researchers published the results of their study in the online journal PLoS One, in an article called “Livestock-Associated Methicillin and Multidrug Resistant Staphylococcus aureus Is Present among Industrial, Not Antibiotic-Free Livestock Operation Workers in North Carolina.”

The study looked at two groups of farm workers and their families. The first group worked on concentrated animal feeding operations (CAFOs), more commonly known as factory farms, where animals were routinely treated with antibiotics. The second group, like MacLean and her farm hands, worked with livestock on pastured farms where animals did not receive antibiotic treatments.

Steve Wing, a co-author of the study and an associate professor of epidemiology at UNC, said both groups of workers had similar rates of Staphylococcus aureus carriers when their noses were swabbed.

But the type of Staphylococcus aureus, commonly known as Staph, was different.

“The workers in factory farms carried strains of Staph that were resistant to antibiotic treatments in the lab,” said Wing. “It had genetic characteristics associated with livestock.”

“Literally 100 percent of our pigs are healthy,” said McClean, who is passionate about the environmental and health effects of giving antibiotics to animals.

“We eat these animals, and antibiotic overuse has repercussions for our health,” said McClean, who sells her meat at the Carrboro Farmers’ Market. “If we disrupt our internal flora and fauna with antibiotic overuse, we run the risk of many health problems, [including] the antibiotics not working when we need them.”

One of Eliza McLean's pigs. Photo courtesy Cane Creek Farm.

One of Eliza MacLean’s pigs. Photo courtesy Cane Creek Farm.

Antibiotic resistance in animals arises when the medicine is given at sub-therapeutic levels for a length of time. In humans, this is similar to not completing your prescribed dose when a doctor gives you antibiotics to fight an infection.

“What happens is, the bacteria that’s left behind is the bacteria that has the strongest resistance to the antibiotics,” Wing said.

Staph includes the well-known super bug MRSA (methicillin-resistant Staphylococcus aureus).

In 2005, MRSA caused about 278,000 hospitalizations for the hard-to-treat infection across the U.S. The bacteria has increasingly been the cause of infections picked up outside of hospital settings; in 2005, doctors reported more than 14 million outpatient visits for suspected MRSA infections in physicians’ offices and emergency departments.

Wing said this new data has far-reaching implications for agricultural and health practices.

“A number of antibiotics used in livestock in production are the same as used to treat people,” said King.  “If we use them for livestock, they won’t be as effective as treatment of human diseases.”

New questions about old practices

Using antibiotics on livestock is a banned practice in Europe, but still common in America. Cows, pigs and chickens are routinely given medicine, the same types of antibiotics humans are prescribed, to keep them healthy in packed living conditions and help them grow faster.

In fact, the FDA states that 80 percent of all antibiotics used in America are used on animals, not people.

Magnified view of methlycillin-resistant Staphlycoccus aureus. Image courtesy the Centers for Disease Control and Prevention.

Magnified view of methicillin-resistant Staphlycoccus aureus (MRSA). Image courtesy the Centers for Disease Control and Prevention

But antibiotics were never intended for this type of use, and as more drug-resistant strains of bacteria surface, health care workers and law makers have been warning of the danger.

“If people are infected with Staph, it can cause serious illness and death,” said King. “These infections are more difficult to treat because the bacteria is harder to treat.”

For MacLean, antibiotic overuse is just another health danger posed by factory farming.

“How the animals are treated impacts us,” she said. “Their excrement feeds into our bodies of water. One of the bad actors on our planet is our agricultural practices.”

Wing said his research aligns with the Preservation of Antibiotics for Medical Treatment Act (PAMTA), a piece of legislation introduced earlier this year by Rep. Louise Slaughter (D-NY).

“There’s not  a lot of study of livestock Staph in the U.S.,” Wing said. ”I can say for myself, I was surprised to see such a striking difference between the two groups of farm workers.”

“This work will continue,” he added.

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