MRSA ST398 in US swine

A little over a year ago I put a post up documenting research out of Canada which found methicillin-resistant Staphylococcus aureus (MRSA) in Canadian pigs. This had also been seen in Europe (with a lot of research coming out of the Netherlands). What I didn't note at the time was that we were gearing up to start some sampling of our own on area swine farms. Some of you saw that we presented the results of that research last year at ICEID and ASM; now the paper is out describing our pilot project in PLoS ONE. (Note: the paper was available earlier, but now they seem to have removed it...keep an eye on that link).

For this research, we swabbed pigs and humans from 2 large swine farming companies in the area. The first ("production system A", PSA) had about 60,000 pigs at any one time; the second (PSB) was smaller, with about 27,000 pigs. These were distributed over several different farms in the area (with several thousand animals on each farm) and are typically age-segregated.

We didn't find any MRSA on PSB, in either the pigs or the people. However, we found quite a lot on PSA, in roughly similar percentages of people and pigs (70% of PSA's pigs, 64% of PSA's people). We carried out molecular typing on all of the human isolates and a subset of the swine, and all that we tested were found to be ST398, the so-called "piggy" MRSA. To our knowledge, this is the first publication of this strain in the US.

I don't want to just repeat what we wrote in the discussion (and hey, the paper's freely available, so just read it!) but suffice it to say, we're busy carrying out a lot of follow-up studies looking at various aspects of zoonotic S. aureus, including lots more studies in pigs but also other animals. A recent publication showed MRSA in a variety of meat products, so while pigs have been a focus, they're obviously not the only potential problem out there.

[Edited to add: Maryn McKenna has covered the story for Scientific American. Ed has an excellent overview as well.]

Tara C. Smith, Michael J. Male, Abby L. Harper, Jennifer S. Kroeger, Gregory P. Tinkler, Erin D. Moritz, Ana W. Capuano, Loreen A. Herwaldt, Daniel J. Diekema (2008). Methicillin-Resistant Staphylococcus aureus (MRSA) Strain ST398 Is Present in Midwestern U.S. Swine and Swine Workers PLoS ONE, 4 (1) DOI: 10.1371/journal.pone.0004258

E DEBOER, J ZWARTKRUISNAHUIS, B WIT, X HUIJSDENS, A DENEELING, T BOSCH, R VANOOSTEROM, A VILA, A HEUVELINK (2008). Prevalence of methicillin-resistant Staphylococcus aureus in meat International Journal of Food Microbiology DOI: 10.1016/j.ijfoodmicro.2008.12.007

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Congratulations on the paper!

By TorontoPDF (not verified) on 23 Jan 2009 #permalink

Congratulations on the publication. Can you tell us more about the different strains of MRSA? How is ST398 different from other MRSA, how many other strains are there, etc?

I followed the "piggy MRSA" link above but the publication is no longer available at CDC. I guess it was in Emerging Infectious Diseases.

Your paper says "MRSA caused 94,000 infections
and over 18,000 deaths in the U.S. in 2005" but leaves us wondering what percentage are caused by the ST398 strain.
I guess we need to read the papers you cite, as well as your paper.

Your paper says "MRSA caused 94,000 infections
and over 18,000 deaths in the U.S. in 2005" but leaves us wondering what percentage are caused by the ST398 strain.

The text of Tara's post gives the answer - 0%. This is the first time this particular strain has been noted in the US, although it is quite common in the Nederlands.

Another paper to be published next month can be found here.

Yep, as Kevin notes, this is the first time ST398 has been found in the US, and little is known about it, period. Most of the studies have come out of the Netherlands, where it's become a big problem in areas that have intensive swine farming. As noted with the New York paper, however, this strain is potentially emerging here in the US.

We are conducting a number of typing studies with porcine MRSA collections in Eastern Netherlands using a new Raman based technology. This method is highly discriminatory and can be performed from culture in minutes. We believe that providing a rapid typing method will facilitate research in this area and provide better and more timely understanding of this issue. We will be at the APHL annual meeting in Anchorage. For mor information, please visit our website.

No, there have been additional cases in the Netherlands and elsewhere, including several in Scotland and also infections with PVL+ ST398 in China.

Blogging your own research. That's very cool!

Inspiration for next time I publish something worthwhile.

Hi Tara,
I do not know if you are aware of all the places this has been reported, but I was reading my recent edition from ASCP, American Society of Clinical Pathologists, of which I am a member, but it has also been published there. My co-workers, other Micro-Biologists as Baylor All-Saints Hospital (a non-profit hospital in Fort Worth, TX) were extremely interested in this research.
Thanks for all you do,
J. Todd DeShong

Cool, thanks. To my knowledge, it's not even been mentioned in literature for the micro/ID societies I'm a member of...

Congratulations, Tara. A blip about your mrsa article made mention in the NY Times.

From the New York Times, March 12, 2009:

"The federal Centers for Disease Control and Prevention reported that by 2005, MRSA was killing more than 18,000 Americans a year, more than AIDS".

So, mrsa, caused by the overuse of antibiotics, is fast becoming the greatest public health threat, with near zero public funding.

Meanwhile, most of those 18,000 so called aids deaths were due to the medications themselves.

Meanwhile, our federal gov has recently thrown 50 billion more down the aids hole, with about half of the funds earmarked to pay for more of the toxic aids meds and the other half thrown down the hiv research toilet which in 25 years has still come up with nothing but a big circle-jerk, and yet no funds at all toward solving the very real problem of epidemic levels of mrsa and nothing toward solving antibiotics overuse.

Also interesting, how mrsa is an equal opportunity infection that equally affects gays, straights, blacks, whites, those in poverty and those who are well off. Yet aids continues to confine itself to those who have run themselves down via prolonged emotional stress, drug addiction, the poverty and malnutrition stricken in the third world, along with other obvious co-factors that have nothing to do with hiv.

Now that the hiv promoters whose unrelenting attacks and harrassment and hatreds on the internet, in the press, on blogs, via emails and even death threats by phone, including portrayals of her as the murderer of her own child on TV, have successfully stressed Christine Maggiore to her final health-breaking point resulting in her death, hopefully they will soon wake up from their ignorance and deal with the very real threat of mrsa instead of promoting the pseudoscience of hiv, the meme that causes aids.

Bravo to Tara for leading the way.

The NY Times article about mrsa is found at the following link;

So, how exactly is it spread from animal to human?
(I raise a 4h hog every I'm gettin kind of scared and wondering what to do to protect myself and kids.)

By cissyvaughn (not verified) on 12 Mar 2009 #permalink

People wishing to follow the research trail about MRSA ST398 might like to check the st398 site link above which has relevant links to over 70 sources organised under 12 categories. More are added regularly.

One more time, just so it sinks into some of the zombies of science:

From the New York Times, March 12, 2009:

"The federal Centers for Disease Control and Prevention reported that by 2005, MRSA was killing more than 18,000 Americans a year, more than AIDS".

Well, how strange, MRSA, growing worse by the year, is at this point killing far more people than AIDS!!!!!!,

Especially considering that most of the AIDS deaths were due to liver failure and other complications directly caused by the fast tracked never placebo tested medications!!!!

And even more especially since in 2005 the CDC also reported that fully half of American hiv positives do NOT even take ANY anti-hiv drugs! And supposedly one fourth of hiv positives do not even know they have it, yet the vast majority are still fully healthy for years and years simply because no-one ever told them they were supposed to get sick and die from aids!!!!

How strange indeed!

But not so with MRSA. Those who have infections from it surely do know because they break out in unhealing sores that soon turn into massive boils as their flesh is eaten away from their bodies. Boy oh boy, they sure know they have it!!! Nobody even needs to tell them!

And to think that MRSA, caused by massive overuse of antibiotics, is now rampant and well on its way to becoming the leading killer in America directly due to the overuse of antibiotics that many of those damned "AIDS DENIALISTS" have been screaming bloody murder about for 20 years!!!!!!!!!!!!

Meanwhile the prestigious hiv researchers continue to fail to find hiv actually killing anyones t cells, and they fail to find any mechanism by which hiv supposedly causes aids, even after 25 long years and even after more than 250 billion dollars has been thrown at it. Far more than has been put to any other scientific endeavor in history!

Can anyone say PONZI SCHEME yet without getting the "DENIALIST" shoe thrown at them?

Nope, not yet!

No wonder poor Christine Maggiorre was even to paranoid to use antibiotics or modern medicine to save her childs or even her own life when she became ill, ESPECIALLY after her very own daughter died just 2 years ago from rare allergic reactions to amoxicillin while the zombies of science just kept blaming the death on her and on hiv and on the lack of aids drugs!!!!!

I think it was Einstein who said: "There are two things that are infinitely unlimited, the universe and human ignorance, and I am not so sure about the universe".

How right he was.... I for one do sorely miss such brilliant minds as his who put a search for truth as the highest priority. Unfortunately, in these dark times, we are surrounded by people who will sacrifice truth opting instead for what they can get instead of what they can give. Science and mankind surely seems to have lost its moral compass, but there is yet hope.....

They say science progresses one death at a time. Lets hope so.

It is time to admit that much in science is broken. The peer review system is broken. Those with little integrity are often calling the shots and in charge of the funds. Conflicts of interest and selfish pursuits are likely about 80 percent of so called modern science. The search for highest truth is on a back burner, while egoic pursuits of position and accumulation of wealth drive most of science and the upper echelons of science positions.

Science and scientific discovery today is at another lowpoint and sinking deeper every day due to the sheer weight of it being so filled with individuals who lack higher values and who pursue truth for the sake of truth and the gifts it can bring mankind.

Hopefully we will soon reach the point where enough Zombie Science really is enough. We are faced with very real and increasing societal problems that we will likely continue to ignore until our entire society is threatened with financial and medical and moral collapse, while fatcat good ole boy conflict of interest infested zombie science researchers, partnered with greedy pharmaceutical companies and bought off politicians continue to ignore and obfuscate higher truth and further drain our American coffers while distracting the naive public's collective attention from the real problems, most of which these bumbling fools and those who have sadly been deluded or decieved by them had created in the first place.

Is this really the best that our best and brightest involved in science can do?

By Most scientists suck (not verified) on 22 Mar 2009 #permalink

Thanks for the info on MRSA pigs and other farm animals. I'm researching this problem for an upcoming story on this subject, to be published soon on our food safety and healthy gourmet eating site ( Will reference your findings and link to your and other sites carrying this important heads-up.
To return the favor: All those interested in food safety might want to check out last Tuesday's (4/7/09) C-SPAN program on this topic hosted at National Press quarters by the Farm Foundation (and repeated on 4/12-13/09). Carol Foreman, Distinguished Food Policy Fellow at the Consumer Federation of America, and Margaret Glavin, a former FDA food safety regulator (still at the FDA), proclaimed the U.S. system tasked with keeping our food supply safe, mostly broken. Both warned that people are being poisoned, and then proceeded to list solutions and insisted on the urgency of their implementation. They voiced particular alarm about the danger posed by the lack of adequate inspection of imported food products.
Two other presenters--one from the meat industry and Scott Horsfall, pres. of the CA Leafy Green Products Handler Marketing Agreement (remember the tainted spinach last year?)-- outlined improvements their respective fields have made and are planning to implement.

By Dina Eliash Robinson (not verified) on 13 Apr 2009 #permalink