Maryn McKenna

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Via Farmworkers, Superbugs Find a Route Away from Drug-Using Farms

September 21, 2014 By Maryn Leave a Comment

Pig farms from the air. Image: Maryn McKenna

Pig farms from the air. Image: Maryn McKenna

One of the persistent questions regarding antibiotic use in meat production, and its effect on the health of humans who live far away from production farms, is: How do the resistant bacteria that result get from one place to another? That is: Most people accept by now that using antibiotics in livestock-raising causes drug resistance to emerge in the systems of those animals, in their guts or on their skin. But whether those newly resistant bacteria leave the farm, and how they make the trip, is both fought over and—despite much investigation—still under-researched.

Some studies have shown that bacteria can move off farms in groundwater, on the feet of flies, and via dust on the wind. What is insufficiently explored—because it is difficult to get large meat-production facilities to cooperate—is whether farm workers themselves are serving as a transport vehicle.

A new study just published (and open-access, so anyone can read it) helps to answer that question. It looks at the possibility that workers on large hog farms are carrying away drug-resistant staph or MRSA, and especially a type of resistant staph — known familiarly as “pig MRSA” and more technically as “livestock-associated MRSA” — that emerged on hog farms a decade ago and is directly linked to farm-drug use.

(If you’ve been visiting Superbug the blog for a while, you might remember pig MRSA; the story of its discovery in a Dutch farmer’s daughter 10 years ago also was told for the first time in Superbug the book. If it’s a new concept to you, you might be interested in this archive here.)

The new study finds that hog farmers are carrying multi-drug resistant livestock-associated MRSA away from the farm and — this is the crucial bit — that their bodies are hanging onto those bacteria, in a way that might allow them to spread, for up to 14 days.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: MRSA, North Carolina, ST398

Denmark: Three Deaths from Drug-Resistant "Pig MRSA"

May 12, 2014 By Maryn Leave a Comment

ICStefanescu (CC), Flickr

Image: ICStefanescu (CC), Flickr

A troubling and also kind of odd story came out of Denmark this weekend. In a court proceeding, a microbiologist has disclosed that three residents of the country who had no known connection to farming died of MRSA infections caused by ST398, the livestock-associated strain of drug-resistant staph that first appeared among pig farmers in the Netherlands in 2004 and has since moved through Europe, Canada and the United States.

If the report is correct — and sources have told me it is, but I’ve seen no data to confirm it — it reinforces the concern that bacteria which become resistant because of antibiotic use on farms can move off farms and affect the health of people who have no connection to farming.

Livestock MRSA has always one of the best cases for establishing that, because the drug to which it showed the greatest resistance, tetracycline, wasn’t used against human MRSA in the Netherlands, but was used routinely on farms — so the only place the strain could have picked up its unique resistance pattern was in pigs. (Here’s my long archive of posts on pig MRSA, dating back to my book Superbug where the story was told for the first time.)
[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, antibiotics, Denmark, food policy, food safety, MRSA, netherlands, Resistance, ST398

Almost Three Times the Risk of Carrying MRSA from Living Near a Mega-Farm

January 22, 2014 By Maryn Leave a Comment

Pig farms from the air. Image: Maryn McKenna

Pig farms from the air. Image: Maryn McKenna

In the long fight over antibiotic use in agriculture, one of the most contentious points is whether the resistant bacteria that inevitably arise can move off the farm to affect humans. Most of the illnesses that have been associated with farm antibiotic use — resistant foodborne illness, for example — occur so far from farms that opponents of antibiotic control find them easy to dismiss. So whenever a research team can link resistant bacteria found in humans with farms that are close to those humans, it is an important contribution to the debate.

A team from the University of Iowa, Iowa City Veterans Affairs, and Kent State University have done just that. In next month’s Infection Control and Hospital Epidemiology, they survey 1,036 VA patients who lived in rural Iowa and were admitted to the Iowa City facility in 2010 and 2011. Overall, among those patients, 6.8 percent were carrying MRSA, drug-resistant staph, in their nostrils. But the patients’ likelihood of carrying MRSA was 2.76 times higher if they lived within one mile of a farm housing 2,500 or more pigs.
[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: animals, antibiotics, colonization, food policy, hogs, MRSA, Science Blogs, ST398

MRSA in UK Turkeys Raises Questions of Communication, Transparency and Risk

December 2, 2013 By Maryn Leave a Comment

Image: OZinOH (CC), Flickr

Two years ago, I celebrated Thanksgiving here on Superbug by announcing some new studies on resistant bacteria being found in turkey meat in the US. That did not go over well; so this year, I saved the bad-turkey news for the post-holiday week. And here you go:

Just in time for our Thanksgiving — and in the ramp-up to English Christmas, for which turkey is a traditional dish — the UK’s Animal Health and Veterinary Laboratories Agency announced that livestock-associated MRSA, drug-resistant staph, has been found in UK poultry for the first time. From their not-very-informative press release:

The Animal Health and Veterinary Laboratories Agency (AHVLA) has identified the presence of Livestock-Associated Meticillin Resistant Staphylococcus Aureus (LA-MRSA) in poultry on a farm in East Anglia… Once the poultry have been slaughtered and sold the owner will carry out cleansing and disinfection of their accommodation to ensure the next birds do not become colonised when they arrive on site. The AHVLA will revisit the farm after depopulation and thorough cleansing and disinfection to determine whether LA-MRSA is still present.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: antibiotics, food policy, food safety, foodborne, Resistance, Science Blogs, ST398, Turkey, UK

More on MRSA on Farms and in Farm Workers, and the Arguments for and Against

July 12, 2013 By Maryn Leave a Comment

Photo: ROIrving/ Flickr

In my last post I promised to catch up on some of the other research that has been published on the flow of MRSA (and other resistant organisms) between farm animals and farm workers as a result of farm antibiotic use.

Before I do that, though, I want to nod toward two other great pieces published on this. First, Mark Bittman  examined this issue closely at the New York Times. And Clare Leschin-Hoar also covered the new research at Take Part. (Bonus: Don’t miss her dissection of the news that a National Geographic photographer was arrested in Kansas after taking pictures of a feedlot — from the air.)

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, animals, antibiotics, food, food policy, food safety, hogs, MRSA, Science Blogs, ST398

"Pig MRSA" Carried by Workers from North Carolina Intensive Hog Farms

July 5, 2013 By Maryn Leave a Comment

Pig farms from the air. Maryn McKenna, Creative Commons License

I saved this post until today to allow everyone to get their holiday hot dogs guilt-free. Now that’s over: An important study has just been published which makes a close connection between the emergence of antibiotic-resistant bacteria, and the use of antibiotics on large-scale conventional hog farms. Bonus: It involves the resistant bacterium MRSA ST398 (known in shorthand as “pig MRSA”), which is widespread in Europe but up to this point has been found mainly in only one state in the US, Iowa. With this paper, the count rises to two(see Update): The study subjects in this paper are hog-farm workers in eastern North Carolina.

A quick explanation of why this is important: “Pig MRSA” is a particular strain of drug-resistant staph that is slightly different from the hospital and community (sports, gym) varieties. It was first spotted in the Netherlands in 2004, in the toddler daughter of pig farmers and in the family’s pigs. Since then, it has spread widely across Europe, not just in agriculture, but in healthcare and in everyday life, and has also been found widely in retail meat.

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. More on that below. (If you want more, here’s an archive of my posts on ST398; the story of its emergence in 2004 and what happened afterward is told in my 2010 book SUPERBUG.)

Now, the study. Quick summary, with more unpacking to follow: Researchers checked livestock-farm workers in North Carolina to see whether they were carrying staph, and also drug-resistant staph. The workers formed two groups: one group worked at conventional hog operations, which routinely use antibiotics, and the other group at antibiotic-free farms. Both groups carried staph and also drug-resistant staph, which would be expected; about 30 percent of the population carries sensitive staph and about 4 percent carries the drug-resistant form. But, the key difference: Workers from the conventional, antibiotic-using farms were many times more likely to carry staph with the specific signature of farm-drug use.

That illuminates a potential occupational risk to the workers — and it also suggests that the workers could be a channel for that farm-influenced bacterium to move off the farm.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, animals, antibiotics, food, food policy, food safety, hogs, MRSA, North Carolina, Science Blogs, ST398

Gene Sequencing Pinpoints Antibiotic Resistance Moving From Livestock to Humans

March 28, 2013 By Maryn Leave a Comment

The antibiotic era was barely 20 years old when people started raising concerns about using the new “miracle drugs” in agriculture. Penicillin first entered use in 1943, streptomycin in 1944, tetracycline in 1948 — and by 1965, the United Kingdom’s Agricultural Research Council was hearing testimony that organisms common in food animals, especially Salmonella, were becoming resistant to the antibiotics being used on the animals while they were alive. By 1969, the UK government had compiled an official report outlining the danger, and by 1973, a task force of the US Food and Drug Administration had concurred, and concluded the only safe action was to withdraw approval to use antibiotics in animals. (At which, as we now know, they would never be successful.)

The policy difficulty regarding this long-recognized problem has never been the emergence of resistant bacteria on farms; no one seriously disputes that resistance emerges whenever antibiotics exert selective pressure on bacteria, killing the vulnerable and opening an ecological niche into which the surviving not-vulnerable can expand. The  sticking point has been the difficulty of proving that those resistant bacteria depart from farms, cross to humans, and cause resistant illness in them. Stuart Levy demonstrated it in 1976, on an experimental farm plot he set up just to make the proof. Most of the rest of the research, though — and after decades, there are hundreds of pieces of research — has been observational and retrospective: Looking at the drugs administered to populations of animals (about which we have very little data), measuring the antibiotic-resistant illness that arises in the human population, and making increasingly sophisticated backward matches between the resistance factors that show up in humans and the drugs that are deployed primarily on farms.

Demonstrating the bacterial traffic prospectively and experimentally, as Levy did, is challenging not just logistically but also ethically. It is difficult to imagine a study design that could trace specific animals, their meat, and their eaters in a large group of free-living humans; and unless you have volunteers, as Levy did, the study would push ethical boundaries as well. But having that lack of definition in the middle of the animal-to-human bacterial flow permits uncertainty — which proponents of continued ag antibiotic use exploit.

A new study of Danish farmers and their livestock may have ended that uncertainty. It is still retrospective, but its observations — using whole-genome sequencing — are so fine-grained that their tracing of the bacterial traffic seems to me to be difficult to challenge.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, animals, antibiotics, food, food policy, MRSA, Resistance, Science Blogs, ST398

Livestock MRSA Found For First Time In UK Milk

December 26, 2012 By Maryn Leave a Comment

This paper almost slipped by me. It was published quietly a few weeks ago, and it’s a little eyebrow-raising. From EuroSurveillance, the open-access peer-reviewed bulletin of the European Centre for Disease Prevention and Control (Europe’s CDC): The ST398 strain of MRSA, better known as “livestock-associated MRSA” or just “pig MRSA,” has been found for the first time in milk in England. (And therefore probably in cows, or at least on farms.)

Apparently there has been an ongoing study looking for any evidence of MRSA in UK cows, possibly because of this news from last year (of which more in a minute). Between last January and July, the program tested 1,500 samples of milk from farms’ bulk tanks — that’s the cooler in which milk from a number of cows is collected until it can be picked up by a truck for processing — and found seven of the samples were contaminated by MRSA. All seven isolates were MRSA ST398, the livestock-associated strain. Three came from one farm, so five farms had MRSA in their tanks.  According to the paper, this is the first discovery of ST398 in the UK other than one finding in horses in 2009.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, animals, food, food policy, milk, MRSA, Science Blogs, ST398, UK

Staph In Pigs And Pig Farmers: The Latest Reports (ICEID 1)

March 12, 2012 By Maryn Leave a Comment

Photo: AndJohan/Flickr

I’m spending the first part of this week at the International Conference for Emerging Infectious Diseases, a biennial scary-disease nerdgasm that is sponsored by the Centers for Disease Control and Prevention, the American Society for Microbiology and other worthy organizations, and in this iteration has drawn about 1,600 participants from more than 50 countries. (You can see the program here. I had planned to live-blog it, but the hotel was just renovated and apparently they built a Faraday cage into it, since connectivity is a painful trickle.)

On Monday’s agenda, among other intriguing talks: Two updates on MRSA, methicillin-resistant S. aureus, among farmers in two states.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: Connecticut, food, food policy, Iowa, MRSA, pigs, Science Blogs, ST398

'Pig MRSA' Came From Humans, Evolved Via Farm Drugs

February 23, 2012 By Maryn Leave a Comment

In the summer of 2004, a 6-month-old girl who lived in the southeastern part of the Netherlands — prime, intensive hog-farming country — went in for surgery for a birth defect of her heart. As is routine in the Netherlands, which has excellent hospital infection control, she was checked before surgery for MRSA, the drug-resistant bacterium that can live on the skin without causing infections and can be unwittingly transmitted from one patient to another. The girl was carrying MRSA, which was a surprise — but the bigger surprise was that her MRSA strain did not render any results on the standard identification test, PFGE.

Looking for a source for the mysterious strain, the hospital epidemiologists where the girl was being treated asked to check her family: father, mother, school-age sibling. They were carrying it. They asked to check the family’s social circle; some of them were carrying it too. Then, flailing about for an answer — the Netherlands has such low rates of MRSA that these persistent findings were really rather odd — the epidemiologists asked what the family and their friends all did for a living, and received the answer that they were all pig farmers. So they checked the pigs, and the pigs were carrying the MRSA strain as well. And if a new MRSA strain in humans was odd, then a MRSA strain in pigs was very odd — because swine have their own varieties of staph, and are not supposed to get S. aureus, the usually human strain that accounts for the “SA” in MRSA.

That summer of detective work (which is told in full in my book Superbug) provided the first sighting of what would come to be called MRSA ST398, or in Europe CC398: a strain which was not quite like hospital MRSA, and not quite like community MRSA, and which carried a distinctive signature of resistance to tetracycline, a drug that is not much used for human MRSA but is routinely used in confinement-style farming. From its first identification, ST398 spread rapidly through Europe, and then into Canada, and then to the United States, being found first in pigs and pig-farm workers, and then in retail meat, and then in people with no connection to farming at all.

The only mystery was where it had come from.

[Read more…]

Filed Under: Science, Science Blogs, Superbug Tagged With: agriculture, animals, food, food policy, MRSA, Resistance, Science Blogs, ST398

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