Effect Measure

Swine and MRSA

The peanut butter/peanut paste ingredient based salmonella outbreak has been in the news lately and we’ve discussed it here (and here, here, here, here, here). There are now about 500 reported cases and six deaths. That’s a case fatality ratio of just over 1%. So what if there were a disease outbreak of 100,000 cases with a case fatality ratio of 20%? I think we’d be pretty alarmed. But it happened in 2005. And it happened in 2006 and 2007 and last year, 2008 And it’s happening, now, too. It isn’t salmonella or or even HIV/AIDS, although it is estimated to kill more people in the US than both put together. It is methicillin-resistant Staphylococcus aureus (MRSA), the difficult to treat antibiotic resistant bacterial infection sometimes called a killer superbug. Originally associated with hospitals, MRSA has now moved into the community. It is a major medical and public health problem and there is still much we don’t know about it, like where it hangs out. Now, thanks to our Scibling blogger (Aetiology) Tara Smith and her colleagues, we know a good deal more. And what they found out is disconcerting.

I’ll let Tara give you the gist:

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.


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. (Tara Smithy, Aetiology; more info and links to the paper [open access] at Tara’s post)

Tara’s paper has been well covered by Ed (Not Exactly Rocket Science) and Mike (Mike the Mad Biologist) here on Scienceblogs.com and by Maryn McKenna at SciAm (Maryn also writes a superb blog devoted to MRSA, Superbug). The ST398 MRSA strain is spreading fast but so far hasn’t been shown to cause serious human disease. The deadly form of MRSA infections comes from hospital strains and presumably they differ from ST398 in virulence factors, genetic elements that make infection with the strain into a serious illness rather than asymptomatic carriage. But virulence factors can move between strains and strains can also evolve to become more virulent.

The subject is well covered in Tara’s paper and the links from my blogging colleagues, so I’ll just add a few observations about things not covered in those places (and if you have any interest at all, by all means visit those links; they are very informative). ST398 was discovered in The Netherlands, then Canada, now the US. It is unlikely it arose de novo in each place. It moved. MRSA has generally been thought of as a problem involving human to human transmission, possibly through fomites (inanimate objects) or directly. Now we need to add the food supply to the equation, both as a mode of transmission and as a reservoir. One of the producers was ST398 free while the other was heavily infected. We need to find out why and incorporate that knowledge into our food safety regulations.

Second, the likely fact that this bug moved internationally means that the US food safety system can’t solve this and similar problems by itself. Unfortunately the current international system is poorly equipped to deal with global problems because it is built on the notion of national sovereignty, which is quickly becoming obsolete in public health (see our posts on this here, here, here, here and here).

It’s time to get the problem of antibiotic resistant organisms under control. That will mean taking on agribusiness, the biggest user of antibiotics and likely one of the main causes of the prevalence of antibiotic resistance. Yes we can.


  1. #1 SrrAB
    January 26, 2009

    Absolutely, revere. It’s difficult to understand why the FDA has not banned the agricultural use of all classes of antibiotics that are currently used to treat humans. As this article demonstrates, the use of antibiotics in agriculture is a problem internationally as well. With the globalization of our food supply, all nations are likely to see antimicrobial resistance increase as a result of antibiotic use in agriculture.

    In Minnesota in 2007, 64% of patients that acquired the food-borne illness of Campylobacter internationally had isolates that were resistant to fluoroqinolones (Ciprofloxacin and Levofloxacin), likely because in countries other than the US, the use of fluoroquinolones is unrestricted in agriculture. Compare this to the 12% of all Campylobacter isolates acquired domestically with fluoroquinolone resistance. I’m going to guess that that’s a significant difference.


  2. #2 Pat Gardiner
    January 26, 2009

    Life is full of strange co-incidences;

    Most Brits are vaguely aware of Paul Revere as one of the heroes of the American Revolution, but probably can’t recall his significance.

    They would regard his cry of “The British are coming!” as somewhat reassuring rather than the reverse.

    His name has been taken and I quote:

    The Editors of Effect Measure are senior public health scientists and practitioners.

    Paul Revere was a member of the first local Board of Health in the United States (Boston, 1799).

    The Editors sign their posts “Revere” to recognize the public service of a professional forerunner better known for other things.

    This group are now showing an interest in MRSA ST398 in Iowa pigs and pig keepers and the origins.

    I have that nasty feeling I’m going to be labelled the British equivalent of Benedict Arnold for trying so hard to warn the Americans of the public health threat being hidden up in Britain.

    They did not listen, but that won’t lessen the crime in English eyes. I’ve already been called a ‘traitor’ several times. It won’t be true but that won’t matter to the guilty.

    Such is the convoluted course of Anglo-American relations.

    On Sunday next, I shall attend church in a tiny market town in rural England with an unexpected cleric. He will begin the service with his usual beginning.

    “As you might have guessed by my accent, I’m an American.”

    He is indeed – a former Colonel in the USAAF – who has long settled in England.

    I think I’ll take my ethics from him.

    Pat Gardiner
    Release the results of testing British pigs for MRSA and C.Diff now!
    http://www.go-self-sufficient.com and http://animal-epidemics.blogspot.com/

  3. #3 Lea
    January 26, 2009

    It isn’t just the abuse and over use of antibiotics in animals alone revere. It’s also the use of growth hormones and animals being fed genetically modified corn.

  4. #4 SrrAB
    January 26, 2009

    Lea, could you please expand on why the use of growth hormones and genetically modified corn is contributing to an increase in methicillin-resistance among porcine staph populations (and their handlers)? I am having trouble making the connection…

  5. #5 Lea
    January 26, 2009

    Didn’t say it was contributing to an increase in methicillin-resistance among porcine staph populations (and their handlers)?
    Sorry if it sounded that way to you.

  6. #6 M. Randolph Kruger
    January 27, 2009

    Lea, pls send me your email address again… it got dumped in the traffic the other day when you sent. Still sending to the old one though.

    Four more days and then enroute. I see Obama wants to talk to the Iranians. Well, good. They will back stab him at the first opportunity, cause him to lose face and well -Its one of the things that I said would happen. Wonder what he will do when they start to try to destabilize Iraq?

    He is burning up the political capital pretty quick and what he isnt, Pelosi and Dirty Harry are.

    Nationalization of the banks…. Hmmmm. Kind of like cap and trade carbon credits that will make Al Gore richer than your wildest dreams.

    But thats okay, he is almost at the 90 day mark for his first 100. Then they are going to tear him apart.

  7. #7 Lea
    January 27, 2009

    Done MRK. Other news in there too.

    SrrAB: Not sure if your remark was on the up and up or if it was sarcastic. But hey, I’ll let it go.
    The point of my remark, which I didn’t explain well enough, was that if “Yes We Can” take on the agribusiness then we had better cover all the bases, not just one.
    The addition of growth hormones were introduced in the late 50’s. It’s my belief it led to boys and girls bodies maturing faster than normal and perhaps it has indeed contributed to the obesity problems so many people are now experiencing.

  8. #8 Jonathon Singleton
    January 27, 2009

    Lea, “The point of my remark, which I didn’t explain well enough, was that if “Yes We Can” take on the agribusiness then we had better cover all the bases, not just one…”

    Yes indeed Lea, I agree… Background reading on homologous recombination: ISIS Press Release 10/03/08 — “Horizontal Gene Transfer from GMOs Does Happen” by Dr. Mae-Wan Ho and Prof. Joe Cummins, from their ISIS website states, “Recent evidence confirms that transgenic DNA [eg. genetically modified corn] does jump species to bacteria…”

    So, I suppose the salient point here is that hyper-evolution is occuring in both viruses and bacteria… Don’t know much ’bout the evolutionary processes of bacteria — my eyes glaze over reading that section of the aforementioned ISIS Press Release from March ’08. But, I do think it’s safe to say one simple thing: both H5N1 and seasonal H1N1 flu is evolving too darn fast compared to the past, knocking out the efficacy of available drugs used to treat us fragile humans. Why is this speed increase happening now? What’s changed in recent years? Simple questions from a simple mind midst the almost daily avian influenza deaths taking place in Asia…


    To: “Nicola Roxon, Federal Australian Minister for Health and Ageing”

    Sunday, December 7, 2008

    Dear Minister Roxon (Federal Minister for Health and Ageing), as you or at least staff from your office in the capital city of Australia already know, I’m an unpaid freelance transgenic pathogen research analyst living in Perth, WA.

    In 1997, midst a 29-year-old THC sabbatical celebrating the completion of a university arts degree, I was watching an SBS tv news item on human H5N1 in Hong Kong (six folk died in this outbreak in Hong Kong’s Special administrative Region from mid-late ’97).

    So how did H5N1 get here?

    “Horizontal Gene Transfer and Recombination” as an evolutionary mechansim — fueled by the unstable viral-promoter, CaMV 35S, in genetically modified crops — has more than a wee bit to do with why a bird virus is stealthily evolving into an antiviral resistant human to human transmissible virus.

    [Further info on the recombination process but — as far as this MBE abstract goes — not the H5N1 viral protein changing cause (GM viral promoters?), “Homologous Recombination as an Evolutionary Force in the Avian Influenza A Virus” by He, C.-Q., Xie, et al. Mol Biol Evol 2009 26: p. 177-187.]

    Canada’s Prof. Joe Cummins was the first to warn, in the 1990s, against using the CaMV 35S promoter or any viral genes in plants cos it had been shown that such viral transgenes in plants could gene flow recombine with historically natural DNA viruses to generate super infectious cross species (transgenic) viruses.

    “Subsequently, the CaMV 35S promoter has been found to substitute for the promoter of many plant and animal viruses to produce infectious viruses.” * Remixed excerpt ISIS Press Release 29/11/04 — “Fluid Genome & Beyond”, from their ISIS website.

    Re: Greenpeace Australia-Pacific — Sign the petition asking federal Health Minister Nicola Roxon to introduce labelling and testing laws for GM food
    Web @ http://www.truefood.org.au/OurRightToKnow/

    Minister Roxon,

    In light of the hyper-evolution of deadly diseases such as H5N1… And also cos of the fact European Union environment ministers are now sceptical of agro-biotech [unscientific self-promotion via sweet smelling, well designed press releases — refer to Greenpeace EU on the EU-GMO-authorisation-system], we, the undersigned, call on the Federal Government, to keep its promises and to protect public health and consumer choice by introducing, and strictly enforcing, legislation to ensure that:

    All GM foods are clearly labelled, including highly processed products such as oils, starches and sugars from GM crops; and meat, milk, cheese and eggs from animals fed GM feed…

    Cheers Then:*) Jonathon

  9. #9 Pat Gardiner
    January 27, 2009

    The link you all need is a mutation to circovirus which took place in the UK 1n 1999.

    The resulting epidemic was swamped by the sucessive classical swine fever (CSF) outbreaks in 2000 and foot and mouth (FMD) in 2001, but continued after these were culled out.

    It still continues to this day and requires large quantities of antibiotics to control. There are continuous problems with pig heath and with antibiotic resistant bugs in the UK.

    British hospitals have high levels of both MRSA and C.Diff. ST398 and NAP1/027/B1 have been found in humans in Britain

    We do know that MRSA ST398 and C.Diff NAP1 are also found in pigs, but no results have been released by the British government.

    It is a classic cover-up of an unusally long duration.

    Pat Gardiner
    Release the results of testing British pigs for MRSA and C.Diff now!
    http://www.go-self-sufficient.com and http://animal-epidemics.blogspot.com/

  10. #10 Lea
    January 28, 2009

    At Maryn McKenna’s site SuperBug there’s an interesting addition to this subject. I’ve included only a portion, click on the link below if you want to read more.

    27 January 2009
    More MRSA in meat, and not just pork

    In my excitement over the paper by Tara Smith and team on Friday, I failed to sufficiently emphasize an important new finding. (I included it in my story for ScientificAmerican.com, but it was toward the end.) I feel it deserves a post of its own, so here it is:

    The Food and Consumer Product Safety Authority of the Netherlands has found MRSA in 12% of 2,217 samples of meat on sale in the country, including not just pork, but beef, lamb, chicken, turkey and game birds, and 85% of the bacterial isolates were the”pig strain” ST 398.

    We have talked before (all posts here) about the potential risk of MRSA in meat, especially ST 398 because it seems to have found a preferred host in pigs. In this study, however, the meat most likely to carry ST 398 was not pork, but turkey, followed by chicken and then by veal, and then by pork.


    Meat sold as “biologic” — that’s “organic,” in the US — had a much lower rate of contamination with ST 398.


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