Maryn McKenna

Journalist and Author

Pigs, antibiotics, and staph where it shouldn't be

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The “third epidemic” of MRSA (drug-resistant staph) — the one that started in farm animals given antibiotics, and subsequently spread to humans — has been contentious since its emergence. This week there are several pieces of new news about it. They’re not likely to solve any of the disagreements, but they’re certainly interesting.

Very quick recap for those coming in late: MRSA, short for methicillin-resistant Staphylococcus aureus, describes strains of staph that have become resistant to most common antibiotics. It’s been gaining ground on us for about 50 years, first in hospitals, then in the everyday world and now in farm animals and farm-workers. Surveillance for it is not excellent, but in various studies, it kills 19,000 Americans, puts about 370,000 in the hospital, and sends possibly 7 million to a primary care visit or ER, and causes billions of additional dollars in health care spending — all in a year. For the most serious infections, there are only a few drugs that still work. It’s the leading organism in the under-appreciated international epidemic of antibiotic resistance. (If you’d like to know more, I wrote a book about it.)

Livestock-associated MRSA — many researchers just call it “pig MRSA,” which makes swine agriculture very unhappy, but the more technical term is MRSA ST398 — was first noted in 2004 in a Dutch toddler being prepped for surgery; then identified in her family and their social circle, all of whom were pig farmers; and then was found in their pigs. Along with the standard suite of MRSA resistance factors — all the beta-lactam antibiotics, which means anything ending in “-illin,” most cephalosporins, the monobactams and carbepenems, and also erythromycin — this new strain was resistant to tetracycline. That was odd, because the Netherlands’ rate of MRSA was so low that they were not bothering to give humans tetracycline for MRSA; but tetracycline was the most common drug given to pigs in large-scale agriculture there. It was proof the organism had been resident in pigs, become resistant as a result of ag antibiotic use, and then crossed to humans. (Yeah, this is all told in the book. OK, no more shilling.)

Since that first finding, ST398 has spread throughout the European Union, into Canada, and in one state in the US, Iowa. (Veterinarians assume it has spread more widely than that, but Iowa happens to be the only state where researchers have looked for it.) It is less common than other strains of MRSA, but it has been identified as the cause of mild skin infections among farm workers, serious hospital infections such as ventilator-associated pneumonia, and life-threatening community infections such as flesh-eating disease. It’s also been found in retail meat in several different countries. (We haven’t yet managed to move my archives over, but there’s a 2-year history of ST398 coverage at my old blog.)

Despite the low number of known cases, MRSA ST398 is important, for several reasons: First, because as those death and illness numbers demonstrate, any additional MRSA is bad news. Second, because MRSA ST398 bridges the human and animal worlds, demonstrating how easily an organism that is resident in animals can cause illness to humans, and also can move across the world with agricultural trade. And third, because its occurrence underlines the consequences of antibiotic overuse in agriculture: If they hadn’t been giving tetracycline to pigs in the Netherlands — a country that, within about a decade, went from small family farms to the largest user of ag antibiotics in the EU — “pig MRSA” might not exist.

So, this week’s update, courtesy again of the Interscience Conference on Antimicrobial Agents and Chemotherapy, or ICAAC: two findings that are somewhat contradictory.

First, a team in the Netherlands wanted to know how much of an infection risk ST398 truly poses. That’s an especially important question in the country where the strain got going. In the Netherlands, which exerts very close control over MRSA overall, certain categories of hospital patients are checked to see whether they are carrying the resistant bug, and if so, put into isolation and treated until they are clear. But some people are considered to be such high infection risks that they are put into isolation presumptively — and since 2007, those categories have included farm workers and veterinarians.

That’s a lot of tests, which means a lot of expense. So the team who presented this week tried to assess whether that isolation and testing are necessary, by measuring how often carriage of MRSA ST398 converts to an active infection. They looked at every MRSA isolate identified in 2009 at two hospitals in the southeast, where pig-raising is most dense, and identified a huge reservoir of carriage of ST398: 61% of the MRSA-positive patients, or 298 out of 486. But of those 298, only 7 developed an infection, and none of them passed the infection to a second patient. The 188 patients carrying hospital MRSA, on the other hand, caused 83 secondary cases — enough to force closure of a department in one of the hospitals. (van de Sande et al., ICAAC 2010)

So while pig MRSA’s easy to acquire, given the right exposure, it may not often cause illness. Problem is, according to a second piece of research discussed this week, when it does, it can be unexpected and devastating.

A coalition of 21 hospitals in Spain wanted to know how many of the MRSA bloodstream infections occurring in their institutions were caused by the community strain of MRSA instead of the hospital strain — something that would signal a change in the epidemiology of what can be a devastating illness. They checked every MRSA bacteremia case from June 2008 through December 2009. They found 324, overall, with 10 of them caused by community strains. But they also found something they didn’t expect: Almost as many, eight of 324, were caused by ST398. (Camoez et al., ICAAC 2010)

This isn’t the first time that MRSA ST398 — an organism linked to agriculture and to spread through farm workers and veterinarians — has been found to cause hospital infections or serious infection. It has caused ventilator-associated pneumonia in Germany and post-surgical infections in Canada.

One of the ways that epidemiology measures the seriousness of an outbreak is to compare it to the expected background occurrence of a disease. In the case of MRSA ST398, that background rate is zero. The strain’s an artifact of the overuse of antibiotics in agriculture. It’s really worth thinking about how many more such organisms we want to produce.

Image: photographer unknown.

Update: The French case — not MRSA but so interesting

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I’m flattered to have as a regular reader Dr. Peter Davies, a professor of swine health and production in the University of Minnesota’s Department of Veterinary Population Medicine. (Disclosure: I worked part-time at U Minn from mid-2006 to mid-2010, but in a different school.) In a comment on my previous post, he points out — perils of reading on a smartphone — an important point where I erred: The staph strain involved in the death of the French 14-year-old was not MRSA, but MSSA, drug-sensitive staph, that had picked up a resistance factor.

Unpacking that a bit: At a minimum, MRSA is resistant to all beta-lactam antibiotics — penicillin, the semi-synthetic penicillins (including methicillin, what the M in MRSA stands for), several generations of cephalosporins, monobactams, and carbapenems. It is also separately, but variably, resistant to macrolides (such as erythromycin), lincosamides (clindamycin), aminoglycosides (gentamicin), fluoroquinolones (ciprofloxacin) and tetracycline.

Livestock-associated MRSA, known as ST398 for its performance on a particular test (multi-locus sequence typing) was first identified as having a tie to pig-farming because it was also resistant to tetracycline, which was being given to the pigs on the farms where the first human carriers worked. (Hence its jocular name, “pig MRSA,” though it’s since been found in other animals.)

The ST398 strain involved in the French girl’s death does not have that broad array of resistance. Chiefly, it was not resistant to beta-lactams, and so can’t be considered MRSA. On analysis, it was resistant to the macrolides, of which the best-known are erythromycin and azithromycin (Zithromax or Z-Pak). Here’s something else intriguing: On another test (spa typing), the ST398 strain in the French girl was one known as t571; the ST398 that has spread from pigs to humans in the European Union, and subsequently to Canada and the United States, is usually t034.

Here’s why this is all so interesting: MSSA ST398 t571 was reported just a few years ago in New York City, in a Bronx community that has close ties to the Dominican Republic, and also in the towns in the Dominican Republic where those Bronx residents come from and visit. (Here’s my initial post on that finding from a medical meeting, and subsequent post when the paper was published.) In that case, the ST398 was fully drug-sensitive — and there was no visible link to pigs, though the authors speculated that livestock, perhaps poultry, might be playing a role on either side of the “air bridge” connecting the two communities.

In the paper (Bhat, Dumortier, Taylor et al., EID 2009, DOI: 10.3201/eid1502.080609), the authors expressed concern that, given staph’s promiscuous ability to acquire resistance — and the fact that ST398 is not regularly surveilled for —  the ST398 in New York could become an undetected resistant strain:

Given ST398’s history of rapid dissemination in the Netherlands, its potential for the acquisition of methicillin resistance, and its ability to cause infections in both community and hospital settings, monitoring the prevalence of this strain in northern Manhattan and the Dominican Republic will be important to understand more about its virulence and its ability to spread in these communities.

And now it appears it has become resistant — but in France, not New York City or the Dominican Republic, and to macrolides, not  beta-lactams. It’s one more reminder of staph’s genius at acquiring genetic defenses, and of how our lack of attention to its mutability and spread continues to allow it to take us by surprise.

News break: "Pig MRSA" ST398 involved in the death of a child?

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The latest postings to the website of the CDC journal Emerging Infectious Diseases include a sad and very troubling letter from physicians in Lyon and Paris, reporting the death from necrotizing pneumonia of a previously healthy 14-year-old girl. That would be sad under any conditions, but here’s what makes the death so troubling: It appears to have been caused by MRSA — but not by the community strain, USA300, that has been implicated in a number of deaths from necrotizing pneumonia. (Several such stories are told in SUPERBUG the book.)

Instead, her death appears to have been caused by infection with MRSA ST398 — the livestock-associated strain that was first noted in pigs raised with antibiotics, and the pig-farm workers caring for them, in the Netherlands 6 years ago, and that has since spread across the European Union, Canada and into the United States. (My 3-year archive of ST398 posts is here.)

This may be the first death associated with ST398, though I can’t say that for sure as I am away from my big computer and working without my database. I’ll update later today and confirm or knock that down.

The physicians say that the girl came in with flu-like symptoms and abdominal pain, was put on IV antibiotics (cefotaxime and amikacin), underwent an exploratory laparotomy that showed nothing, and shortly afterward developed acute respiratory distress and was put on a vent. A chest X-ray was shadowy on both sides. She went rapidly downhill and died 6 days later.

On analysis, the staph strain infecting her was ST398; there was no indication where she had picked it up. The strain had an unusual characteristic: It possessed the ability to make the cell-destroying toxin Panton-Valentine leukocidin, PVL for short, a genetic trick that until now has been a property only of community MRSA strains such as USA300. Though its role is disputed, PVL has been linked to community MRSA’s ability to start infections on intact skin, and to the cellular damage that destroys children’s lungs in cases of pneumonia caused by USA300. Until now, ST398 has been PVL-negative.

The physicians’ letter is short and there’s much more to find out about this case. But if the report and analysis are correct, this is bad news. One of the repeated themes in the 50-year evolution of MRSA has been its ability — all staph’s ability — to promiscuously swap and share the bits of DNA that confer resistance and enhance virulence. Another, since the emergence of ST398, has been the potential peril of a staph strain adapting and mutating in the millions of farm animals around the world that are routinely given antibiotics — and that for the most part are not checked to see whether they harbor resistant organisms. If this report (and my interpretation) are correct, then those two trends are converging in a way that cannot bode well.

Antibiotic use in animals: The feds move, a little

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(You leave the country for a few days — I spoke at a conference in Brussels, which was was lovely, thanks for asking — and all kinds of news breaks out. So, sorry to be late on this, but it’s an important issue.)

Last week, the Food and Drug Adminstration took the first (baby, mincing, tentative) steps to address the problem of antibiotics being used in animal agriculture, not to treat disease, but to make animals grow up to market weight faster. This practice — variously called subtherapeutic dosing, growth promotion, and “for production purposes” in the FDA’s exceedingly careful language — has been fully banned in the European Union for 4 years, and some aspects of the practice have been banned longer.

The simple reason for the ban: There’s decades of good science and real-world experience showing that it contributes to the development of drug-resistant organisms in farm animals and the farm environment, organisms that leave farms in the animals and in their manure, and also contaminate the environment beyond farm borders via leakage into groundwater and dust blowing off manure lagoons.That movement off the farm is critical because many of the drugs used in agriculture are the same, or close analogs, of drugs used in human medicine; so resistance that develops on the farm endangers human health as well. (MRSA ST398, livestock-associated MRSA, is the latest example of this. Find a long archive of posts on ST398 here.)

Just to be clear, growth-promoters don’t treat disease; they’re given to healthy animals solely for the purpose of getting them up to sale weight and to market faster. The ways in which antibiotics are given to livestock to treat or prevent disease have their own issues, but those are not part of the FDA effort. (Historical note: The growth-promoting effect of trace amounts of antibiotics was first recognized in 1947, when scientists at Lederle were looking for something to do with the leftover fermentation mash from the manufacture of chlortetracycline, fed it to chickens, and discovered they thrived on it. Stuart Levy’s The Antibiotic Paradox tells this story in detail.)

In human medicine, when we give antibiotics to people who are not sick with a bacterial illness, we call it inappropriate use — and aim massive education campaigns at the practice in an attempt to dial it down. In contract, the animal side has had a free pass for a long time, to the extent that it remains unclear how many antibiotics are used in farming in the US (best estimate: about 70% of all antibiotic use in the US per year), and there is no organized surveillance that would look at what organisms are emerging in animals from that use.

The FDA has been trying to put curbs on growth promoters since the 1970s, always without success; the lobbying against it, by agriculture and also by pharmaceutical interests, is reliably intense. There’s been a parallel effort in Congress to limit the use in animals of drugs that have close analogs in human medicine, via the Preservation of Antibiotics for Medical Treatment Act, or PAMTA, authored by Rep. Louise Slaughter (D-NY), Congress’s only microbiologist. PAMTA has been introduced in several Congresses but this year finally gained some traction. Last year, the Obama administration signaled, in testimony by then-new assistant FDA commissioner Joshua Sharfstein, that it might be friendly to the idea of dialing back on growth-promoter antibiotic use, and it looked as though the long logjam might finally be broken.

Well, OK: Not broken, exactly. Just shifted a little, and maybe showing a tiny bit of light.

On Tuesday, the FDA released a “draft guidance” that proposes animal ag do two things: stop using growth-promoting subtherapeutic dosing, and administer antibiotics to animals under the supervision of a veterinarian. That’s the good news.

The bad news: It’s only a guidance, not a regulation. In other words, it has no force in law. It’s more like a request — though in a press conference last week, Sharfstein suggested it might also be a shot across agriculture’s collective bow:

We have the regulatory mechanisms and the industry knows that. But we are also interested in what things can be done just voluntarily that they would do them. And I think it’ll be interesting to see how the industry responds to this and how – what direction their comments take. …We’re not handcuffed to the steering wheel of a particular strategy at this point. We really want to understand what people think. And but we’re also – I’m not ruling out anything that we could do to accomplish these important public health goals. (Transcript)

Reactions to the FDA announcement were predictable — effectively “No science, more research needed”: Here’s the National Cattlemen’s Beef Association, the National Pork Producers Council, and a standing statement by the Animal Health Institute. (Supporting the FDA move: the Pew Charitable Trusts, the New York Times.)

The draft guidance stays open for public comment for 60 days, until Aug. 30. The required Federal Register posting is here, with the mailing address. Electronic comments can be left at Regulations.gov; the docket number for the guidance is FDA-2010-D-0094; 33 comments have been posted already.

Antibiotic resistance in food — some governments pay attention

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Folks, I told you Tuesday about a Congressional hearing on antibiotic resistance, featuring NIAID Director Dr. Anthony Fauci and CDC Director Dr. Thomas Frieden. Not much new was said, but it’s encouraging that the hearing was held at all. (Fauci testimony here, Frieden here.)

Coincidentally, constant reader Pat Gardiner of the UK alerted me to a gathering being held on the same day in Ireland, by the quasi-government agency SafeFood—which reports to the North-South Ministerial Council of Ireland, which deals with whole-island issues under the Good Friday agreement, which is more about the Irish political structure than you probably ever wanted to know.

The conference was titled Antimicrobial resistance and food safety and featured government officials and academic researchers from across Ireland. Here’s the agenda, and here’s the press release with the names of key speakers. Even more important, here are links to a report on antibiotic resistance in food that Safefood released in advance of this conference: executive summary and whole thing.  I especially recommend from p.25 in the big report for an accessible discussion of the connections between ag antibiotic use and human health. Key quote among many:

The majority of the evidence acquired through outbreak and epidemiological investigations of sporadic infections, field studies, case reports, ecological and temporal associations and molecular sub-typing studies support the causal link between the use of antimicrobial agents in food animals and human illness. A few papers have questioned this but these have not survived detailed scrutiny.

It’s refreshing to see a government body engage seriously with this emerging issue, which we’ve been talking about for, well, years now, on this blog (sometime this month we passed our 3-year anniversary). I wish, wistfully, that the government doing the discussing was ours.

A blog reaction so perfect I want to print the whole thing…

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(…but I won’t, because it’s not fair use or good blogger behavior. But I want to!)

Melissa Graham of Chicago had a great corporate life — and then she re-evaluated, became a chef and caterer, and began organizing in Chicago for sustainable local food, farmers’ markets, and a family-friendly food system. She blogs at the food and food-policy blog The Local Beet. And she’s written a reaction to SUPERBUG that not only completely gets the book, but is emotional and thoughtful and moving besides.

She says, in part:

Before reading Superbug, the question of confinement raised animals was an ethical one for me – whether the misery inflicted upon animals and, for that matter, the humans working in those facilities by the putrid conditions outweighed the need to eat cheap meat. Even the environmental degradation resulting from the inevitable careless management of CAFOs seemed a distant and intangible casualty. For me, Superbug has changed the argument from one of ethics to a moral imperative. In every hamburger of unknown origin, I see Tony Love’s face or even worse that of Carlos Don IV.

Carlos was another healthy kid who left on a school trip to the mountain and returned with a 104°F fever. The first doctor diagnosed Carlos with walking pneumonia so his mother kept him home bundled and hydrated until she realized that he was beginning to hallucinate. She rushed Carlos to the hospital and the doctor’s ultimately diagnosed his condition as MRSA. A long slow death march ensued during which Carlos’s lungs dissolved and clotting choked off the blood to his lower intestines, legs and arms. In two weeks, he was dead.

After reading Carlos’s story late in the evening, I woke a bewildered little locavore from a dead sleep to scrub his hands clean. I hugged him as tightly as I could.

…[recently] I had the pleasure to hear Ruth Reichl speak and she implored the audience to stop eating confinement raised animals. As she put it, if everyone stopped buying them and eating them, the practice would be history. Knowing what I now know, I think it’s our moral duty.

To give the post the traffic it deserves, please go here.

Catching up to MRSA news (not about me)

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Constant readers: I’m looking forward to having the breathing space to get back to in-depth blogging. Meanwhile, though, news is zipping by — so here’s a quick list of recent things worth reading.

“Cows on Drugs” — a superb history of the 30-year-old fight to get unnecessary antibiotics out of food animals. Note, written by a former commissioner of the Food and Drug Administration, not exactly a wild-eyed radical:

More than 30 years ago, when I was commissioner of the United States Food and Drug Administration, we proposed eliminating the use of penicillin and two other antibiotics to promote growth in animals raised for food. When agribusiness interests persuaded Congress not to approve that regulation, we saw firsthand how strong politics can trump wise policy and good science.Even back then, this nontherapeutic use of antibiotics was being linked to the evolution of antibiotic resistance in bacteria that infect humans. To the leading microbiologists on the F.D.A.’s advisory committee, it was clearly a very bad idea to fatten animals with the same antibiotics used to treat people. But the American Meat Institute and its lobbyists in Washington blocked the F.D.A. proposal.

Antibiotic resistance in your kitchen, playroom, car... — After years of begging from health advocates, the FDA and EPA are taking a second look at the chemical compound triclosan, an antibacterial that is put into, well, almost anything you can name: soaps, hand sanitizers, cutting boards, toys. Triclosan is suspected of interfering with hormone regulation in the body, and also increases resistance in organisms in our environment. (When I ask you to use hand sanitizers that contain only alcohol or salts, not antibacterials, triclosan is one of the things I’m thinking of.) The FDA will report its findings in a year. I’d rather see it happen sooner, but it’s a great move.

No progress on hospital-acquired infections — The Agency for Healthcare Research and Quality, part of the Department of Health and Human Services, has published its 2009 National Healthcare Quality Report. The news is not good. To quote the agency’s own language: “Very little progress has been made on eliminating health care-associated infections.” This is all hospital-acquired infections, not just MRSA, but MRSA is a leading organism. The ugly details:

  • Post-operative bloodstream infections up 8%
  • Post-operative catheter-associated urinary-tract infections up 3.6%
  • “Selected infections due to medical care” up by 1.6%
  • Bloodstream infections as a result of central lines unchanged.

(NB, three professional organizations — the Infectious Diseases Society of America, the Society for Healthcare Epidemiology of America, and the Association for Professionals in Infection Control — put out a statement in response to this report saying it “presents an outdated and incomplete picture on healthcare-associated infections (HAIs) in our healthcare system.” The gist of the statement seems to be that they’ve got better numbers coming… soon. When there’s actual data, I’ll let you know.)

SUPERBUG on Capitol Hill

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Constant readers, I’ve been shamefully absent from the blog, but with reason, since I’ve been traveling promoting the book. There was a pretty interesting opportunity this week that I wanted to tell you about: I was asked to be part of two Congressional briefings in Washington, DC Wednesday, addressing the overuse of antibiotics in agriculture and the contribution that makes to the emergence of resistant organisms such as MRSA. I went specifically to tell the story of the emergence of MRSA ST398, which we’ve been talking about for years here.

The briefings (FYI, “hearings” are for Congresspersons, “briefings” are for their staff) were cosponsored by the Pew Charitable Trusts, Union of Concerned Scientists, American Public Health Association, Infectious Diseases Society of America, and the nonprofit Keep Antibiotics Working.

Here’s Pew’s announcement, here’s the UCS version, here’s a write-up from the Washington Examiner, and here’s a longer one from the site Spectrum Science.

"Pig MRSA" causing human infections

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Hi, everyone. Apologies for dropping out of sight! As SUPERBUG’s publication draws closer (and it’s very close now), I keep finding new tasks that I have do to. Last week’s was to go to New York to shoot a video for the Simon & Schuster website — and while there, I got caught in Snowpocalypse, got delayed coming home, and picked up a nasty cold. So I’m a bit behind.

But there’s exciting news tonight to start us up again: “pig MRSA,” ST398, causing human infections in Canada and Denmark.

“Infections” is important, because up til now, most evidence for  the spread of MRSA ST398 in humans has been through detection of colonization, the symptomless carriage of MRSA on the skin and in the nostrils. The first finding of ST398 in the Netherlands was via colonization; so was its first identification in humans in Canada, and also in the United States just about a year ago.

[Read more…]

Farming and antibiotics – and voices from the ag side

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The whole issue of how antibiotics get used in agriculture — as growth promoters, as prophylatic treatment to prevent spread of infection within a farm, or as true treatment — is intensely controversial. For a sense of how farmers feel embattled, read the comments to this entry at FairFoodFight on whether there is a distinction between “Big Ag” and “small ag.” and consider that the PAMTA legislation I posted about in December, which would require veterinarian oversight of farm use of antibiotics,  has been strongly opposed by agricultural interests every time it has been introduced. (Large-farm use of antibiotics, let me remind you, has been concluded to be the driver behind the emergence of “pig MRSA” ST398.)

But I recently ran across two pieces online that I want to draw your attention to, because they demonstrate that thinking in agriculture about antibiotic use is not monolithic, and may be changing. Both were posted on the same site, the Illinois-based Agri-News Online.

[Read more…]

Back again to MRSA in animals, and spreading to humans

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There are two new reports out regarding new findings of “pig MRSA” ST398 (about which we have talked a lot; archive of posts here.)

First, researchers from the Complejo Hospitalario Universitario de Vigo and Complejo Hospitalario de Pontevedra, both in Pontevedra in northwest Spain, report that they have identified that country’s first human cases of infection with ST398. (It was only last fall that Spain reported the first identification of the strain in animals.)

The age of the three patients was 59, 82, and 83 years, respectively. Two patients owned pigs and the other a calf. Two patients were diabetic and were hospitalized because they developed skin and soft-tissue infections by MRSA ST398. The third patient had bronchitis and the strain was isolated from a respiratory secretion submitted to the laboratory from an outpatient clinic. The three patients had had multiple hospital admissions in the last 12 months.

Tellingly, the researchers spotted these particular isolates (out of 44 analyzed at the two hospitals in 2006) because they were resistant to tetracycline. Tetracycline resistance is not common among community strains of MRSA, because the drug isn’t the first-line choice for skin and soft-tissue infections; and when it is given, it’s usually for a short course, so the drug does not exert much selection pressure on the bug. But tetracycline is a very common animal antibiotic, and tetracycline resistance is a hallmark of ST398; it is one of the factors that led the Dutch researchers who first identified the strain to take a second look at the bug.

Second, researchers from several institutions in Italy report a very troubling case of ST398 infection that produced necrotizing fasciitis — better known as flesh-eating disease. [Read more…]

Warning on ST398: Monitor this now

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Drawing your attention: I have a story up tonight at CIDRAP on a new paper by Dr. Jan Kluytmans, a Dutch physician and microbiologist and one of the lead researchers tracking “pig MRSA,” ST398. (All past stories on ST398 here.) It’s a review paper, which is to say that it summarizes key existing findings rather than presenting original research.

Still, it’s important reading because Kluytmans is one of the few scientists who have some history with this bug and understand how quickly and unpredictably it has spread across borders and oceans, from pigs to other livestock, to pig farmers and veterinarians, into health care workers and hospital patients who have no known livestock contact, and now into retail meat in Europe, Canada and the United States.

Take-away: A plea and warning for better surveillance, so that we can track not only the bug’s vast range, but also its evolution as it moves into new ecological niches — including humans who are buying that retail meat and possibly becoming colonized with it as they prep it for cooking in their home kitchens.

To honor fair use (and in hopes you’ll kindly click over to CIDRAP), I won’t quote much, but here’s the walk-off:

Because the novel strain has spread so widely and has already been identified as a cause of hospital outbreaks, it should not be allowed to spread further without surveillance, Kluytmans argues.”It is unlikely that this reservoir will be eradicated easily,” he writes. “Considering the potential implications of the reservoir in food production animals and the widespread presence in meat, the epidemiology of [MRSA] ST398 in humans needs to be monitored carefully.”

The cite is: Kluytmans JAJW. Methicillin-resistant Staphylococcus aureus in food products: cause for concern or case for complacency? Clin Microbiol Infect 2010 Jan;16(1):11-5. The abstract is here.

Antibiotics in animals – a warning from the poultry world

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Constant reader Pat Gardiner guided me to an enlightening post at the website of the agricultural magazine World Poultry that questions the routine use of antibiotics in food animals. It’s written by Wiebe van der Sluis, a Netherlands journalist from a farming background, founder of World Poultry and also the magazines Pig Progress and Poultry Processing.

The Netherlands, let’s recall, is the place where MRSA ST398 first emerged, and also the place where that livestock-MRSA strain has caused the most serious human cases and triggered the largest changes in hospital infection-control practices. In the Netherlands, swine farmers and veterinarians are considered serious infection risks because of their exposure to animals, and are pre-emptively isolated when they check into hospitals until they can be checked for MRSA colonization.

Van der Sluis takes seriously the tie between the use of antibiotics in animals and the emergence of MRSA:

Although most of the time MRSA is linked to pig production, it is also related to the veal and poultry industry. The industry, therefore, cannot shrug its shoulders and move on if nothing was wrong. In this case it would be wise to redefine the term prudent use of antibiotics. Time is up for those who use antibiotics to cover up bad management, poor housing conditions or insufficient health care. The standard rule should be: Do not use antibiotics unless there is a serious health issue and no other remedy applies. Veterinary practitioners, who usually authorise producers to use antibiotics, should also take responsibility and prevent unnecessary antibiotic use and the development of antibiotic resistance in animals and humans.

It’s unusual in the US context so hear someone so immersed in agriculture speak so candidly about antibiotic use. It’s refreshing.

Wednesday a.m.: Congressional briefing on antibiotics in livestock – live-tweeted!

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Folks: On Wednesday 2 December, at 9:30 a.m. EST, Rep. Louise Slaughter (D-NY) will host a Congressional briefing about antibiotic use in food animals. As a reminder, Rep. Slaughter is an MPH and Congress’s only microbiologist, and the chief sponsor of PAMTA, the Preservation of Antibiotics for Medical Treatment Act that proposes restricting antibiotic use in animals to therapeutic uses under the guidance of a veterinarian and phases out “growth promotion” with sub-therapeutic doses, which consumes millions of pounds of antibiotics every year, many of them close analogs to human drugs.

Appearing at the briefing along with Rep. Slaughter are leaders of efforts that have produced an important string of reports on antibiotic overuse — the Pew Commission on Industrial Farm Animal Production and the Extending the Cure project of Resources for the Future:

  • Michael Blackwell, DVM, MPH–former Vice Chair, Pew Commission on Industrial Farm Animal Production; Assistant Surgeon General, USPHS (ret.); Former Dean, College of Veterinary Medicine, University of Tennessee, Knoxville, TN.
  • Robert Lawrence, MD–Director, The Johns Hopkins Center for a Livable Future, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
  • Ramanan Laxminarayan, PhD, MPH–Senior Fellow, Center for Disease Dynamics, Economics, and Policy, Resources for the Future, Washington, DC
  • Robert Martin–Senior officer, Pew Environmental Group; former Executive Director, Pew Commission on Industrial Farm Animal Production, Washington, DC
  • Lance Price, PhD– Director, Center for Metagenomics and Human Health, Translational Genomics Research Institute, Flagstaff, AZ

Here’s a post explaining the importance of this issue from the blog of the Center for a Livable Future, a Johns Hopkins University research group that has produced some of the most mportant papers on leakage of antibiotic-resistant bacteria and antibiotic residues from CAFOs (“confined” or “concentrated” “animal-feeding operations” — very, very large-scale farms). And here’s some video on the issue from last summer from Lou Dobbs Tonight.

Because the event Wednesday is an informational briefing, not a hearing, I can’t find any link for a live webcast. (I’ll update if I find one.) But the hearing will be live-tweeted by the staff of the Center for a Livable Future (@LivableFuture) at the hashtag #CLF09. BLOGGERS: They will take tweeted questions toward the end of the hearing, ~10:45 a.m. — use the hashtag.

"Pig MRSA" in the EU – long-awaited survey

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It’s not very likely that people will be eating much pork today — OK, maybe some pancetta in the Brussels sprouts — and that’s good, because there’s lots of news today about MRSA in pigs.

(In fact, there’s a ton of news just this week. Make it stop.)

The European Food Safety Authority has published a long-awaited, European Union-wide survey looking for the presence of MRSA in pigs. Here’s the key points: Investigators found MRSA on 1 out of 4 farms where pigs were being raised and in 17 of the 24 EU states. (Two non-member states were included in the analysis.)

Strictly speaking, this is not a survey of MRSA in pigs; the study samples not the pigs themselves, but the dust in pig-raising sheds. The sites were 1,421 breeding farms and 3,176 farms where pig are raised to slaughter age. By far the most common strain was MRSA ST398, though other strains were detected, including some known human strains. The prevalence in various countries went from a low of 0 to as high as 46% of farms. (Highest, in descending order: Spain, Germany, Belgium, Italy, Portugal. The Netherlands, where St398 was first identified, had a prevalence of 12.8%. Countries reporting no MRSA: Bulgaria, Cyprus, Denmark, Estonia, Finland, Hungary, Ireland, Latvia. Lithuania, Luxembourg, Sweden, the United Kingdom, Norway and Switzerland.)

The report closes by recommending comprehensive monitoring of pigs for MRSA, as well as monitoring of poultry and cattle.

About the potential of ST398 crossing to humans, it has this to say:

In humans, colonisation with MRSA ST398 originating from pigs has been identified as an occupational health risk for farmers and veterinarians and their families. Although MRSA ST398 represents only a small proportion of the total number of reports of human MRSA infections in the EU… in some countries with a low prevalence of human MRSA infection, CC398 is a major contributor to the overall MRSA burden.
In most cases, colonisation with MRSA ST398 in humans is not associated with disease, although clinical cases associated with MRSA ST398 have been reported. MRSA ST398 can be introduced into hospitals via colonised farmers and other persons in a region with intensive pig farming. Therefore, MRSA ST398 may add substantially to the MRSA introduced in health care settings. However, it seems that the capacity for dissemination in humans (patient-to-patient transmission) of livestock-origin MRSA, in particular ST398, is lower as compared to hospital-associated MRSA).
… Food may be contaminated by MRSA (including ST398), however there is currently no evidence for increased risk of human colonisation or infection following contact or consumption of food contaminated by ST398 both in the community and in hospital.

Britain’s Soil Association, which pressed for the study to be done, has released a statement quoting the food safety agency warning that the testing method may have underestimated MRSA’s presence on farms, and warning that if ST398 is not yet in England, it is certainly soon to arrive. Germany’s Federal Institute for Risk Assessment also released a statement, admitting that ST398 in German pig stocks is “widespread.”

The report is here, executive summary here, and press release here. All well worth reading.

New MRSA pig strain in China

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Via Emerging Infectious Diseases comes the full version of a piece of research I posted on in September that was presented at the London conference Methicillin-resistant Staphylococci in Animals: Veterinary and Public Health Implications. A new MRSA variant — not ST398 — has been spotted in pigs in China.

Luca Guardabassi and Arshnee Moodley of the University of Copenhagen and Margie O’Donoghue, Jeff Ho, and Maureen Boost of the Hong Kong Polytechnic University report that they found a pig-adapted MRSA strain in 16 of 100 pig carcasses collected at 2 wet markets in Hong Kong. By multi-locus sequence typing, the strain is ST9, previously found in pigs in France; by PFGE, they fall into categories that tend to carry the community-strain cassettes SCCmec IV and V.

Here’s the bad news: This strain possesses resistance factors that resemble human hospital-associated MRSA more than they do ST398.

Twelve isolates displayed a typical multiple resistance pattern, including resistance to chloramphenicol, ciprofloxacin, clindamycin, cotrimoxazole, erythromycin, gentamicin, and tetracyline. The remaining 4 isolates were additionally resistant to fusidic acid. … All isolates were negative for Panton-Valentine leukocidin and susceptible to vancomycin and linezolid.

The further bad news, of course, is that this is being found in Hong Kong, adjacent to China, which is the world’s single largest producer of pork, raising tens of millions of tons of pig meat per year. Most of the pigs sold in Hong Kong come from the Chinese mainland, not from the SAR. Pig surveillance for MRSA in China is practically non-existent (which is not much of a criticism since it does not exist in the United States, either). A human infection with ST9 has already been recorded in Guangzhou, the province adjacent to Hong Kong.

The question, for this strain as for all MRSA strains in pigs, is what is its zoonotic potential? Here again, the news is not good. According to Maureen Boost, who presented this research at the London conference, the isolates were obtained by the researchers from intact heads from butchered pigs; the researchers took the snouts to the lab and and swabbed them there. Pig snout happens to be a desirable meat in China; it is bought in markets, taken home and made into soup. Boiling in broth would probably kill MRSA bacteria — but home butchering of a pig snout could pass the bug on to the human cutting it up, or to that human’s kitchen environment, long before the snout ever got into the pot.

The cite is: Guardabassi L, O’Donoghue M, Moodley A, Ho J, Boost M. Novel lineage methicillin-resistant Staphylococcus aureus, Hong Kong. Emerg Infect Dis. 2009 Dec. DOI: 10.3201/eid1512.090378

 

New reports on animals, food, MRSA ST398

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Well, constant readers, didn’t expect to be gone *that* long. Many apologies. There was a good reason — actually, several: I attended a journalism meeting, and spoke at a second meeting. But most important, I received, marked up, and returned the galleys of SUPERBUG. Yes, it’s really starting to look like a book now. There will be things to share, soon.

Meanwhile, I’ll try to roll out some of the many, many pieces of news and research related to staph that have emerged in the past few weeks. Today: News on animals, and our old opponent, MRSA ST398.

First: A team from the Universidad de La Rioja reports in the Journal of Antimicrobial Chemistry the first finding of MRSA ST398 (“pig MRSA,” archive here) in food in Spain. They tested 318 raw meat and wild-game samples (chicken, pork, veal, lamb, turkey, rabbit, game bird, wild boar, deer, hare) and found ST398 and other MRSA strains in 5 of them, an incidence of 1.6%. The authors write: “Although MRSA prevalence in raw food is low, the risk of its transmission through the food chain cannot be disregarded.”

Importantly, one of the other strains found in the meat of these animals is an uncommon variant, ST125-t067, that has already been implicated in large numbers of hospital infections in Spainand is resistant to ciprofloxacin (Cipro), erythromycin and a third antibiotic, tobramycin, in addition to the usual suspects. The other non-ST398 strain is ST217, which is a variant of a long-known hospital strain, and is also resistant to Cipro, a very valuable drug for skin and soft-tissue infections. So it appears the contamination may cross both ways, from animals, and to animals as well.

No link, but the cite is: Lozano, Carmen, et al. Detection of methicillin-resistant Staphylococcus aureus ST398 n food samples of animal origin in Spain. Journal of Antimicrobial Chemistry. e-pub Oct. 21 2009 AOP doi:10.1093/jac/dkp378

Next: If the prevalence of ST398 is so low in food, why do we care? We care because of where those organisms go next — into hospitals, among other places. A Dutch/German team that includes the original identifier of ST398 in humans are reporting that they have found an association between the density of pig-farming in parts of Germany and the probability that patients admitted to hospitals will be carrying ST398 with them, creating a possible source for nosocomial infections. R. Kock and colleagues screened 1,600 pigs on 40 German farms, and also reviewed screening results for every MRSA-positive patient admitted to the University Hospital-Munster from 2005 through 2008. They found ST398 on 70% of the farms, and also found that ST398 represented 15% of the MRSA isolates at the hospital in 2005, rising to 22.4% in 2008. The key association: The patients carrying St398 were more likely to have contact with pigs in their daily lives, and also with cattle, than patients who had other forms of MRSA or no MRSA at all.

The cite for that paper: Kock, R. et al. Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) among pigs on German farms and import of livestock-related MRSA into hospitals. European Journal of Clinical Microbiology and Infectious Diseases, e-pub Aug 25, 2009. DOI 10.1007/s10096-009-0795-4

And finally: How do you stop the evolution and spread of antibiotic-resistant organisms in livestock? One good way is to stop giving teh livestock antibiotics in the first place. In a column at the Huffington Post, Laura Rogers, project director of the Pew Campaign on Human Health and Industrial Farming, takes on the oft-repeated assertion that you can’t farm without them without risking the lives and market place of your livestock, and offers the example of Denmark, which did ban antibiotics in animals, and which has healthier, more profitable livestock as a result:

American agribusiness often has criticized Denmark’s 1998 ban on antibiotics, calling it an outright failure. But compelling new research presented by a Danish scientist earlier this year showed the opposite, revealing that antibiotic use on industrial farms has dropped by half while productivity has increased by 47 percent since 1992. Danish swine production has increased from 18.4 million in 1992 to 27.1 million in 2008. A decrease in antibiotic-resistant bacteria in food animals and meat has followed the reduced use of these vital drugs.

New news on MRSA and animals

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Constant readers, I’ve been behind the Great Firewall of China for two weeks, unable to post. (Apparently Blogger is not always unavailable there, but access has tightened up in advance of the National Day celebrations on Oct. 1.) I left with a file of things to post in my spare time — and so now we’re way behind, with lots to catch up on.

Latest news first, though. A few days ago, an intriguing conference was held in London: Methicillin-resistant Staphylococci in Animals: Veterinary and Public Health Implications. It was co-sponsored by the American Society for Microbiology and the European Society of Clinical Microbiology and Infectious Diseases, and it was the first conference ever convened to examine the behavior in animals of MRSA and other staph species, including our old friend, ST398.

I have the abstracts (which have not otherwise been published), and wow, there was a ton of news.

Here’s the biggest: An investigation by a team at University of Iowa (the same group that first identified ST398 in pigs and pig farmers in the United States) found significant amounts of MRSA in pigs and in human workers on 4 out of 7 conventional farms, but no MRSA on 6 organic farms. MRSA was present — as a colonizing organism, not causing illness — in 23% of the 168 pigs sampled on the conventional farms, and 58% of 45 humans who worked on those farms. “These results suggest a significant number of U.S. swine may be colonized with MRSA, adding to the concern about domestic animal species as a reservoir of this bacterium,” the abstract says. “Furthermore, occupational exposure to these colonized pigs may spread the bacteria from the farm to the community via a high number of colonized swine workers.” (Author: Abby L. Harper, MPH, University of Iowa)

A partial list of the other findings announced:

  • MRSA ST398, which emerged as an animal and human pathogen in the Netherlands, is now causing human colonization and illnesses in other countries. Denmark, which like the Netherlands has a very low background rate of MRSA, has detected 109 cases since 2003, 35 of them with actual infections. Two of the infections were very serious: one pneumonia in a newborn baby, and one septic arthritis in an adult that led to sepsis and multi-organ failure. (J. Larsen, National Centre for Antimicrobials and Infection Control, Denmark)
  • Meanwhile, the Netherlands — which conducts routine screening for MRSA carriage on hospital admission — has seen its annual count of MRSA detections rise from 16 per year between 2002 ad 2006 to 148 per year between 2006 and 2008, with 81% of the current cases due to ST398. (M. Wulf, PAMM Laboratory, the Netherlands) UPDATE: Coilin Nunan of the Soil Association in the UK corrects me (thanks, Coilin!): This study covers only the southeastern pig-farming areas, or about 40% of the MRSA cases in the country.
  • MRSA ST398 spreads from infected to uninfected pigs during transport to slaughterhouses and while being held at slaughterhouses. (E. M. Broens, Wageningen University, the Netherlands)
  • More than 15% of slaughterhouse workers who handle live pigs — but none of those who handled pig carcasses after slaughter — were carrying MRSA 398, and 25% of environmental samples such as dust taken from different parts of slaughterhouses were carrying the organism as well. (B. A. van Cleef, RIVM [National Institute for Public Health and the Environment], the Netherlands)
  • Along with the pig-origin ST398, recognized human strains of MRSA can also colonize pigs, according to a study on one Norwegian farm, but human strains are less successful at persisting in pigs and tend to die out after months. (M. Sunde, National Veterinary Institute, Norway)
  • Animal-origin MRSA is rising in China, the world’s largest producer of pork, but the problematic strain there is ST9, not ST398. That MRSA strain was found on 5 out of 9 farms in Sichuan province in mainland China, and in 33.5% of 260 pigs slaughtered in Hong Kong, where more than 90% of pork comes from the mainland. (J. A. Wagenaar, Central Veterinary Institute, the Netherlands; and M. V. Boost, Hong Kong Polytechnic University)
  • And an intriguing finding for those concerned about humane slaughter methods: Broiler chickens were significantly more likely to carry MRSA, and transmit it to slaughterhouse workers, if they were killed by the traditional method of electrical shock followed by throat-slitting, and less likely to carry or transmit the bug if they were killed by carbon dioxide asphyxiation, which has been held out as a more humane method of killing. (M. N. Mulders, RIVM [National Institute for Public Health and the Environment], the Netherlands)

UPDATE: I’m still a bit jet-lagged and forgot to mention that, of course, we have a long archive of coverage of ST398 and other strains in animals. Find them here.

Non-medical use of antibiotics: A whole new problem with ethanol

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Constant readers, we’ve talked frequently about the emerging recognition that the enormous use of antibiotics in agriculture is fueling the development of resistance, both directly in the case of specific organisms such as MRSA ST-398, and indirectly in that it pushes the evolution of resistance factors that bacteria then trade amongst themselves. (For a superb overview of the antibiotics/agriculture problem, see this article in the June issue of the Johns Hopkins (University) Magazine. Hopkins is the home of the Center for a Livable Future, which is doing excellent research on this issue.)

And we’ve also talked about the related issue of antibiotic residues elsewhere in the environment, in sewage and wastewater supplies.

But here’s a whole new peril: Antibiotic resistance generated by ethanol production, that vast corn-based industry that has been pitched as a homegrown biofuel alternative to foreign oil.

Food-policy blogger (and farmer and chef) Tom Philpott has been doggedly following this story for more than a year at Grist. And in a study published last month the Institute for Agriculture and Trade Policy brings some important numbers-based analysis. The gist of the problem is this:

  • Ethanol production uses yeast to convert corn starches into alcohol
  • Bacterial contamination, usually by lactobacilli, can hijack the process and covert the starches to unusable lactic acid instead
  • To prevent that from happening, ethanol producers dose their corn mash with antibiotics
  • Because contamination is frequent and persistent, producers use increasing amounts of antibiotics to overcome bacteria that have become resistant
  • After ethanol is extracted, the mash residue remains tainted with those resistant bacteria and with antibiotics — including penicillin, erythromycin and streptogramin (an analog of the human antibiotic Synercid)
  • The dried mash residue is sold to farmers as livestock feed, exposing livestock to resistant bacteria and dosing them with unsuspected additional antibiotics as well.

If there is any good news in this, it is that (according to the IATP), some of the faltering ethanol industry is aware of the problem and working on it, with about 45% of plants now working on non-antibiotic alternatives. The bad news is that 55% — more than 90 of the 170 ethanol facilities in the United States — are not.

Media round-up: recommending MRSA stories

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By chance — or is it because interest is really picking up? — a couple of worthwhile stories on MRSA have been published almost simultaneously:

  • For when the science gets wonky: Environmental Health Perspectives has an excellent lay-language explanation of how drug resistance emerges and spreads — with gorgeous graphics!
  • For when yet another drug doesn’t work: Scientific American covers development of new antibiotics, and even more important, development of new ways of creating antibiotics.
  • For yet more depressing news about MRSA in meat: Prevention adds to the discussion of MRSA in the food supply with a “special report” review. Constant readers who have been following along as we’ve drilled into this topic over the past two years won’t find a lot new, except for an intriguing account of an outbreak of MRSA in an Arkansas chicken plant (in which the bug went disappointingly untyped, so we don’t know whether it was a human strain or ST398). The story hits on issues we have talked about here: Surveillance for MRSA in animals is non-existent, practically speaking, and when the bug is found, investigation falls between human and animal health agencies. It’s a longer than usual story for Prevention, and should bring the knotty food-policy questions around MRSA in meat to a new audience.