Maryn McKenna

Journalist and Author

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

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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…]

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

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

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

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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.

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

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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.)

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

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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.

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Gene Sequencing Pinpoints Antibiotic Resistance Moving From Livestock to Humans

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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.

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Livestock MRSA Found For First Time In UK Milk

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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.

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

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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.

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

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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.

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Drug Resistance in Pork: More Going On Than Appears

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A paper released recently, by the University of Iowa team that is the lone US research group tracking “pig MRSA” ST398, caused a ripple. (It came out while I was at ScienceOnline and it’s taken me a while to catch up.) The paper compares the occurrence of MRSA, drug-resistant staph, on various cuts of retail pork from pigs that were raised either conventionally in confinement, with routine use of antibiotics, or in an alternative rearing scheme with no antibiotics. (NB: Not “organic,” despite what some headlines said; that’s a separate issue of USDA licensure.) The team found that both conventionally raised and antibiotic-free meat carried MRSA, both the human-associated kind and the pig-adapted kind.

The TL;DR over the past week has been: There’s just as much resistant bacteria on drug-free meat as there is on conventional meat, so why spend the money — or raise the alarm over farm antibiotic use?

My interpretation is a little more nuanced. But my takeaway is that, in its underlying data, the study proves what campaigners against ag antibiotic use keep saying: that once you use antibiotics indiscriminately and drive the emergence of resistant organisms, you have no way of predicting where that resistance DNA will end up.

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More MRSA Found In U.S. Retail Meat (Turkey, Too)

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There are two new studies out that confirm, once again, that drug-resistant staph or MRSA — normally thought of as a problem in hospitals and out in everyday life, in schoolkids, sports teams, jails and gyms — is showing up in animals and in the meat those animals become.

The strain of staph that shows up in farm animals, known as “livestock-associated” MRSA or MRSA ST398, first emerged in pigs in the Netherlands, and has been widely identified in retail meat in Europe. (You can find a long archive of posts on ST398 here, and more here.) But that same strain has been difficult to identify in the United States. That may be due in part to the U.S. having a uniquely massive epidemic of community-associated MRSA, far larger than in any other country, which likely both obscures any animal epidemic from detection, and possibly also fills the ecological niche that livestock-associated staph might otherwise occupy. But, it must be said, there’s also remarkably little political will to look for livestock-associated MRSA (though the U.S. Department of Agriculture has now funded a study).

Nevertheless, individual investigators keep trying, and when they look for the pathogen, they find it, such as in these studies from May and this one from April. Now, two other teams have as well.

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More MRSA, in milk: A new strain in cows and humans

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Despite the massive AIDS anniversary this week, I was expecting to write about the EU E. coli outbreak next. But there’s striking new news on MRSA that makes it worth putting off E. coli one more day. I’m traveling many time zones away from home, though, so this will be quick.

Researchers in England and Denmark have announced they have found a never-before recorded variant of MRSA in cow’s milk in England that has already caused human infections in England, Scotland and Denmark, and researchers in Ireland have simultaneously announced that they have found the same strain in hospitalized patients there as well.

Here’s how this unfolded:

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MRSA in meat: How much? Which? And more bad news.

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(Sorry for the radio silence, constant listeners. It’s been a challenging few weeks at Casa Superbug, with a death in the family and the chaos afterward of catching up to the rest of life. But back now, with some interesting stuff planned for later this week.)

Last week was the General Meeting of the American Society for Microbiology (ASM). This is the conference at which, several years ago, Tara Smith’s team at the University of Iowa first announced they had found MRSA ST398 in pigs in the United States, so it always bears watching for new MRSA news, and this year it didn’t disappoint.

First: I’ve complained persistently because the federal system that monitors antibiotic-resistant bacteria in animals and food, NARMS (National Antimicrobial Resistance Monitoring System) doesn’t include MRSA among the pathogens that it tracks. It is possible that might be changing — because at ASM, a team from the Food and Drug Administration reported the results of a pilot study that looked for MRSA in retail meat in the US and found it.

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Farm Antibiotics: 'Pig Staph' in a Daycare Worker

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It’s been just about seven years since an alert epidemiologist in the Dutch town of Nijmegen identified an aberrant strain of MRSA, drug-resistant staph, in a toddler who was going in for surgery to fix a hole in her heart. The strain was odd because it didn’t behave normally on the standard identifying tests, and because it had an unusual resistance factor — to tetracycline, a drug that it should not have been resistant to, because the Netherlands had such low rates of MRSA that tetracycline wasn’t being used against the bacterium there.

Pursuing the source of the strain, researchers at Radboud University found it in the toddler’s parents and sister, and in the family’s friends. Not knowing where else to look, they asked what the parents and their friends did for a living; discovered they were all pig farmers; and went to their farms, and checked the pigs, and found it being carried by them, too. Suddenly, that strange resistance pattern made sense: The Netherlands uses more antibiotics in pig agriculture than any other country in the European Union, and the drug that it uses the most is tetracycline. Clearly, the aberrant strain — known as MRSA ST398 for its performance on a particular identifying test — at some point had wandered into pigs, become resistant to the drugs being given to the pigs, and then crossed back to humans, carrying that new resistance factor as it went.

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Multi-Drug Resistant Staph in 1 in 4 Meat Samples

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Much of the contentious debate over abuse of antibiotics in farming boils down to a couple of simple questions: Whether resistant organisms that arise on farms because of antibiotic use leave the farm, and whether, once they do, they reach human beings.

A piece of research due to be released this morning in the journal Clinical Infectious Diseases helps answer both those questions. (I received an advance copy under embargo; I’ll put up the link when the journal posts it. here’s the link to the full-text pdf.)

A team of researchers from Arizona bought meat and poultry in five cities across the United States, tested them for bacteria, and found this: 47 percent of the samples contained the very common pathogen Staphylococcus aureus, and 96 percent of those isolates were resistant to at least one antibiotic. Of more concern: 52 percent of those staph isolates were resistant to at least three antibiotics that are commonly used in both veterinary and human medicine.

That is: Roughly one in four packages of meat and poultry from across the United States contained multidrug resistant staph. [Read more…]

Opposing industrial-scale pig farming — in Europe

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Well, wow. National legislators stand up to oppose the use of tax revenues to subsidize large-scale confinement pig farms out of concern for food safety and antibiotic resistance, declaring that they are “going to war in defense of pigs.”

In Europe, though.

At the European Parliament today, three national representatives — Janusz Wojciechowski of Poland, José Bové of France and Dan Jørgensen of Denmark — declared their opposition to industrial-scale swine agriculture, positioning themselves for a fight over the European Union’s Common Agriculture Policy, which is up for revision this summer.

Jørgensen represents the country that has done the most to place controls on agricultural antibiotic use; Bové is a farmer and political organizer who famously destroyed a McDonald’s by driving a tractor through it; and Wojciechowski is the son of pig farmers who wrote on his blog today:

Chcemy poruszyć sumienia posłów i doprowadzic do likwidacji tego typu “fabryk miesa” w Unii Europejskiej, no czywiscie takze w Polsce, gdzie takich fabryk jest juz ponad sto.
Chcemy doprorowadzic do tego, aby wielkie fermy nie były wspierane środkami europejskimi, aby wstrzymać lokalizacje nowych obiektów, po czym stopniowo likwidować te, które już istnieją.
Chcemy, żeby na miejsce fabryk miesa powróciła normalna hodowla świń.
We want to move the conscience of members and lead to the liquidation of this type of “meat factories” in the European Union, also in Poland, where such plants are already over a hundred.
We want to ensure that large farms are not supported by the European funds to stop the locations of new facilities, then gradually eliminate those that already exist.
We want “meat factories” returned to normal breeding of pigs. (via GoogleTranslate)

As I’ve written before (long archive here and here),the MRSA strain ST398 arose on Dutch pig farms in 2004, among pigs that had been given prophylactic doses of antibiotics, especially tetracycline. It has since spread through the EU, Canada and the United States, affecting not only farm workers and veterinarians, but also hospital patients with no connection to agriculture.

(Self-promotion alert: This may be a good time to tell you that my book SUPERBUG: The Fatal Menace of MRSA, which tells the full story of the emergence and spread of ST398, has just been released in paperback.)

In advance, this morning the trade paper Farming UK wrote this about the planned European Parliament announcements:

(Members of the European Parliament) will hear evidence that European taxpayers’ money is being used by the European Bank for Reconstruction and Development, together with Common Agriculture Policy payments, to subsidise industrial pig farming even though there is increasing concern over the impact on human health. With a vote this summer over reforms to the Common Agricultural Policy, MEPs will come together to take a stance against the crisis in agriculture with critically low prices for pork, poor labelling, and widespread disregard for animal welfare laws.

MEPs and NGOs will condemn the overuse of antibiotics in factory farms which has led to the emergence of antibiotic-resistant bacteria such as MRSA and ESBL E. coli. A recent report by the Dutch Food Standards Agency estimated that one third to one half of all antibiotic resistance in human diseases in the Netherlands derives from farm antibiotic use. American scientists recently found that flies and cockroaches from intensive pig farms carry bacteria resistant to the same antibiotics routinely used in pig farming, and warned that the insects were likely to be able to spread the disease from the farms to local people.

The event was co-organized by Tracy Worcester, who is both a British aristocrat and director of a documentary, Pig Business, that has not yet been shown in the US. Here’s its trailer:

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In both medicine and agriculture, Europe has been ahead of the US in addressing concerns about antibiotic resistance. This morning’s announcements are yet more evidence of just how far ahead they are.

Flickr/VickyTGAW/CC

Farm worker infections with MRSA — the first numbers

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Since the first identification in 2004 of MRSA ST398, also known as “pig MRSA” or livestock-associated MRSA (archives of posts here and here), that drug-resistant organism has been found being carried asymptomatically by farm workers and veterinarians, and causing illness in health care workers, hospital patients, and people with no known ties to agriculture. One of the persistent data gaps, though, has been whether farm workers themselves have been made sick by it.

It’s a difficult question to answer for a nested set of reasons: First, in most of the states, MRSA (methicillin-resistant Staphylococcus aureus, or drug-resistant staph) is not a reportable disease; that is, a doctor who diagnoses it in a patient is under no obligation to tell any public health authority about that patient’s case. And second, the testing required to distinguish livestock-associated MRSA from community-acquired or hospital-acquired is not something that primary-care medical personnel have access to; you have to go to a state laboratory or an academic medical center to do the appropriate molecular typing. Those tests are expensive to perform, and their results primarily are useful to public health, not to individual medical practitioners. So finding out where that nascent epidemic is going has been unusually challenging.

Comes now a team from the University of Iowa — the same team that first identified ST398 in pigs and pig-farm personnel in the United States — to start to fill the gap. [Read more…]

"Pig MRSA": New human infections in France

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It’s one of the touchiest topics under the broad category of antibiotic resistance: Whether the drug-resistant organisms that emerge on farms as a result of antibiotic use stay on farms, or pose a risk to humans who have no connection to agriculture.

That drug resistance emerges under any selective pressure is basic biology: Resistance is an inevitable process. That they emerge on farms when antibiotics are used broadly — that is, in growth-promoting or prophylactic ways, not to treat disease in individual animals — really isn’t in dispute any more. It’s now a question of economics and politics, not science. (See this bibliography, stretching back to 1969; and the news I broke yesterday of FDA’s estimate of US farms using almost 29 million pounds of antibiotics last year.)

So the argument over farm antibiotic use now tends to focus on whether the resistant organisms that emerge on farms are only an issue within a farm’s confines, or rather pose a broader human health threat — and that’s where the continuing story of the “third epidemic” of MRSA becomes so important. Recapping, this is a strain known as MRSA ST398 that emerged in pigs and passed to pig farmers in the Netherlands in 2004, subsequently spread across the European Union, and crossed to Canada and then to the United States. (Key posts on ST398: here, here, here and this archive at my old site. Yes, it will be moved soon, promise.)

Most of the identifications of MRSA ST398 in humans, including those first identifications above, were colonizations, the term for symptomless carriage of staph in the nostrils and on the skin; in other words, it wasn’t making people sick. News of actual illnesses has been rare — especially illnesses among people who have no contact with farming, such as the post-surgical infections found in Canada earlier this year.

But they’re getting a little less rare, as demonstrated by a letter just posted ahead-of-print to the journal Clinical Infectious Diseases. It recounts the finding, via annual surveys of bloodstream infections, of four cases of ST398 in four different hospitals in France. One may have been due to animal exposure. Three were hospital-acquired.

Examination of patient histories revealed exposure to animals in 1 case, a fatal idiopathic community-acquired bloodstream infection in an 84-year-old man who lived on a farm at which 1 pig was being raised. The remaining cases were hospital-acquired and included 1 case of catheter-associated infection observed in a 58-year-old man with advanced multiple myeloma, 1 case following elective digestive tract surgery in a 69-year-old woman, and 1 case following cardiac surgery in a 68-year-old man.

There’s an especially interesting thing about these cases. In Europe and the US, ST398 has particular characteristics: It is resistant to tetracycline (the drug most commonly given to pigs) and does not manufacture the toxin Panton-Valentine leukocidin or PVL, which is suspected to be a cause of community-strain MRSA’s uncommon virulence. (See this story, from the book SUPERBUG, of how PVL-positive pneumonia almost killed a toddler.) The strain in the French cases, though, does manufacture PVL, and shares some virulence characteristics with the dominant community strain, USA300. It is less like the European strain of livestock-associated MRSA and more like a livestock-associated strain that appears to be emerging in China, ST9 (more on that here).

The argument against the significance of these cases is likely to be that they are, again, just one data-point, and may be just rare and random. That is worth considering. But it is also worth considering that they continue to be found.

And, also, that the community epidemic of MRSA was first flagged in a discovery of 25 cases in children in Chicago back in 1998, a finding that was also dismissed at the time as rare and random — and that grew into an epidemic of millions of cases a year.

(H/t to constant reader Pat Gardiner for flagging this paper for me.)

Cite: van der Mee-Marquet N et al. Emergence of Unusual Bloodstream Infections Associated with Pig-Borne–Like Staphylococcus aureus ST398 in France. Clin Infect Dis. (2011) 52 (1): 152-153. doi: 10.1093/cid/ciq053

Image via Flickr user johnmuk under CC

Alarm over "pig MRSA" — but not in the US

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There’s some new news out — along with a fair amount of public reaction — regarding “pig MRSA” or, to use the technical term, MRSA ST398, the “third epidemic” strain that emerged in pigs in the Netherlands in 2004 and has since appeared, in animals, retail meat, and humans, across the European Union, in Canada, and in the United States. (My last post on it is here, and a long archive of my posts on it starts here.)

I wish I could say the attention to ST398 was being paid in the United States, where there is almost certainly more MRSA in livestock than has been recorded, given that the only published surveillance, from 2009, covered only Iowa and Illinois. Unfortunately, there is still no indication that federal agencies have any intention to test for the presence of the organism in animals or in meat. In fact, the major surveillance mechanism for drug-resistant organisms in meat animals, retail meat and meat-eaters in the US, the National Antimicrobial Resistance Monitoring System or NARMS, doesn’t test for MRSA at all; it handles only enteric or gut-borne bacteria such as Salmonella and Campylobacter. (NARMS IS shared among three agencies: the CDC handles drug-resistant foodborne bacteria in humans, the FDA looks for the same bacteria in food, and the USDA looks for those bacteria being carried by livestock.)

Instead, as so often seems to happen with antibiotic resistance, the country paying attention is in Scandinavia — in this case, Denmark. The annual report from Denmark’s surveillance scheme, DANMAP (Danish Integrated Antimicrobial Resistance Monitoring and Research Programme) is out. Denmark does surveil for MRSA, and here’s what they found: 13% of pigs, at slaughter, were positive for MRSA ST398.
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