Maryn McKenna

Journalist and Author

Bill in Congress: “Preservation of Antibiotics for Medical Treatment” Act

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Important news for anyone concerned about the spread of “pig MRSA” ST398: Rep. Louise Slaughter (D-NY) and Sen. Edward Kennedy (D-MA) have introduced a bill that would restrict important classes of antibiotics for use against disease only, taking them out of the realm of subtherapeutic use or growth promotion in agriculture. The bill would allow the use of the antibiotic classes for disease in animals as well as in humans; the intent is to preserve the drugs’ effectiveness for as long as possible.

The text of the bill, the Preservation of Antibiotics for Medical Treatment Act of 2009, is here.

A Reuters story in which Slaughter predicts the bill will have a difficult time is here; she has introduced it several times in the past decade, but it has never made it through.

Support from the Pew Commission on Industrial Farm Animal Production is here. An earlier version was supported by the American Academy of Family Physicians here.

The National Pork Producers’ Council’s response is here.

(Hat tip to Barry Estabrook at Politics of the Plate and to Melinda Hemmelgarn, the FoodSleuth.)

“Sick as a pig” – from ST398

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Constant readers, I am at the annual meeting of the Society for Healthcare Epidemiology of America, where there is a lot of news about MRSA in hospitals. I hope to post on that over the next few days.

In the meantime, though, I want to pass on several pieces of news about ST398, the “pig strain” that we have talked so much about.

First, the Soil Association, the British organic/sustainable farming group that has done much work elucidating the spread of ST398 and making the link between that bug and antibiotic use on farms, has released an online documentary about ST398 called Sick as a Pig. You can watch it here, and here is the Soil Association’s press release:

…40% of Dutch pigs and up to 50% of Dutch pig farmers are now carrying the new strain, which is also spreading to the wider population. Although this type of MRSA was first detected in humans in the Netherlands as recently as 2003, it now causes almost one in three cases of MRSA treated in Dutch hospitals.
It is not yet known whether any British pigs are affected by the new strain of MRSA (called ST398) since the results of testing, which was required by the EU and carried out in 2008, have not been made public.
Several countries have already published the results of their own tests revealing significant levels of MRSA in national pig herds. The European Food Safety Authority has said that, ‘It seems likely that MRSA ST398 is widespread in the food animal population, most likely in all Member States with intensive animal production’.

Second, here is a paper from last fall that somehow slipped by me: in the CDC journal Emerging Infectious Diseases, a report of two cases of ST398 infection in men in Sweden. Neither had any contact with farming or animals.

The first patient, a previously healthy 36-year-old male physiotherapist, sought medical care in March 2006 for a small abscess in his axilla. Culture of the abscess grew MRSA. Presence of mecA gene was confirmed by PCR. During the next 2 months, furunculous [sic] developed twice, caused by the same strain. His youngest child, adopted from China, had been found to be MRSA positive (throat, perineum, and a small wound) a month earlier during routine screening for adopted children. During subsequent screening of the family, the older sister, adopted from South Korea, was also found positive (throat). Both parents were negative for MRSA at that time, which suggests that the father was newly infected when his abscess developed and that he had not acquired the strain abroad. Also, spa typing indicated that the children carried different strains from that of the father and from each other (t286, t1434). Subsequent screening of family members for MRSA on several occasions found only the father to be repeatedly positive.
The second patient, a 43-year-old male clerk, also previously healthy, sought medical attention during the summer of 2007 for a MRSA-infected elbow wound. Follow-up examination determined that he carried MRSA also in the perineum and in a chronic external otitis eczema. He was later hospitalized for a larger abscess that required surgical drainage. His family members reported no symptoms and were thus not screened for MRSA.

Of note, the men’s strain (ST398, t034) carried the two genes that express the toxin PVL, which is unusual in ST398, though characteristic of CA-MRSA USA300, the dominant community strain in the US. The role that PVL plays is very controversial: Some research groups believe it is responsible for the rapid tissue destruction that can accompany USA300 infection (in penumonia and some soft-tissue infections, for instance), while others vociferously disagree.

New York Times takes up “pig MRSA” ST398

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Constant readers, I know that many of you are very interested in ST 398, the “pig strain” of MSRA that has caused both mild and life-threatening human infections in Europe and has been found in retail meat in Canada and on farms and in farmers here in the Midwest. So I just want to bring to your attention that New York Times columnist Nicholas Kristof takes up the topic today, in the first of two promised columns: Our Pigs, Our Food, Our Health.

In today’s piece, he describes an apparent epidemic of skin and soft-tissue infections in a pig-farming area of Indiana that caught the attention of a local family physician, who subsequently died.

What we’d need to know, of course — and may never know, given that the investigation may have ended with the doctor’s death — is what strain of MRSA those local folks had. They may have ST 398, picked up if they worked on farms, or if it migrated out of the farms via groundwater or dust or flies. Or they may have USA300, the human community-associated strain, which in some areas is astonishingly common — a fact that most people don’t appreciate if they have heard only about the invasive child-death cases or the outbreaks in sports teams.

The full archive of posts on MRSA in animals is here and stories only about ST398 are here.

More MRSA in meat, and not just pork

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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.

So what does all this mean? It’s still probably too early to tell: Recall that the first isolations of this bug were in 2004, there have still been only a few papers on it, and this finding by Smith and team is the first identification of the strain in the United States. (Though not in North America, as it was identified in Canada in 2007.) It seems likely that ST 398 may have found a niche in other food animals, and that it contaminates the meat when the animals are slaughtered.

The consensus among the Dutch, though, is that this is an effect of the use of antibiotics in food animals. The romantic image of the Netherlands is as a cute little collection of postage-stamp family farms, but the reality, especially in the southeast of the country, is that they have substantial industrial-sized farms housing thousands of animals on relatively small properties. The only way to grow animals efficiently under such conditions is to keep very close tabs on potential illness, and liberally deploy antibiotics when necessary. (NB, I am not talking here about sub-therapeutic, growth-promoting use, but rather prophylactic antibiotics, given to an entire herd when a certain percentage of the herd shows sign of illness.) Evidence for this, according to the current study’s authors: Meat sold as “biologic” — that’s “organic,” in the US — had a much lower rate of contamination with ST 398.

There are still very few reports of human illness from ST 398, though of those reports, some are quite serious, including wound infections and endocarditis. The concern here, as the researchers interested in it have been saying from the start, is that someone will inadvertently colonize themselves with the organism by touching their eyes or nose while handling meat contaminated with ST 398. Colonization does not necessarily lead to disease, but it does lead to a far greater pool of organism potentially spreading unmonitored through human and animal populations, swapping resistance and virulence factors as it goes.

So, you know what I’m going to say: Wash your hands, wash your hands, wash your hands.

Appearing tonight at SciAm.com

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Folks, last summer I told you about the very exciting though disturbing development of ST 398 MRSA — the “untypable” Dutch strain that originated in pigs and spread to humans — being found in pigs in the US for the first time.

But here’s the brand-new second half of that story: It was found in pig handlers as well, on a set of linked farms — a closed production system that takes pigs from birth to just before slaughter — in Iowa and Illinois.

The full study has just been published, in the online Public Library of Science journal PLoS One.

And I have a story describing the research and the background — and the alarming spread of ST 398 in Europe — up tonight at ScientificAmerican.com.

The cite is: Smith, TC, Male, MJ, Harper, AL et al. Methicillin-Resistant Staphylococcus aureus (MRSA) Strain ST398 Is Present in Midwestern U.S. Swine and Swine Workers. PLoS ONE 4(1): e4258 doi:10.1371/journal.pone.0004258

UPDATE: Lead author Tara Smith talks about the paper at her own blog, Aetiology. And for good measure, her Science Blogs sibling (AKA “scibling”) Ed Yong discusses the paper at Not Exactly Rocket Science.

“Pig MRSA” in New York City – via the Dominican Republic?

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Folks: Back in October, I broke the news for you of an intriguing poster presentation at the ICAAC meeting. It revealed the discovery of ST 398, the anomalous staph strain found in pigs, pig farmers and health care workers in Europe, in residents of a Dominican-immigrant neighborhood in northern Manhattan, and also in the Dominican Republic.

Because there is so much traffic back and forth between those neighborhoods, the authors theorized that people are providing an “air bridge” for the bacterium — though they were unable to say whether the bug is moving from the Dominican Republic to the United States, or vice versa.

I was unable to link to that presentation at the time, because it was a meeting poster – yes, literally a poster, the authors stand by it to discuss it with anyone who wanders by. However, now it has been published as a paper, in the CDC journal Emerging Infectious Diseases; and because it is a CDC journal, the full text is available free online here.

Just to underline, despite my headline above, the strain found in NYC was not MRSA: It actually is MSSA, drug-sensitive staph. The ST 398 found in Europe, Canada and the American Midwest is MRSA. The authors hypothesize that the NYC strain is at risk of becoming MRSA also.

To see the multiple posts in this blog about MRSA ST 398 and other strains in the food chain, food animals, and pets, go to the labels under the time stamp on this post, and click “animals” or “food.”

The cite for the paper is: Bhat M, Dumortier C, Taylor B, Miller M, Vasquez G, Yunen J, et al. Staphylococcus aureus ST398, New York City and Dominican Republic. Emerg Infect Dis. 2009 Feb; [Epub ahead of print]

MRSA in meat in Louisiana: pig meat, human strain

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On Nov. 3, I posted on an enterprising group of TV stations in the Pacific Northwest who had retail meat in four states tested for MRSA. I said at the time that it was the first finding of MRSA in meat in the US that I knew of.

Turns out that I was wrong by three days. On Oct. 31, the journal Applied and Environmental Microbiology published an electronic version of a study that they will be printing in the paper journal on some future date. Journals do this when a finding is so important or timely that it should see the light immediately, rather than wait through the additional weeks or months of print production.

And this finding is certainly timely. Shuaihua Pu, Feifei Han, and Beilei Ge of the Louisiana State University Agricultural Center have made what appears to be the first scientifically valid identification of MRSA in retail meat in the United States. But — and this is an important point — it is not the swine strain, ST 398, that has been found in meat in Canada and Europe, and in hospital patients in Scotland and the Netherlands, and in pigs in Iowa; and in humans in New York, though that strain was drug-sensitive.

Instead, what the researchers found (in 5 pork and 1 beef samples, out of 120 bought in 30 grocery stores in Baton Rouge, La. over 6 weeks in February-March 2008) was USA300, the dominant community MRSA strain, and USA100, the main hospital-infection strain. In other words, they found meat that had been contaminated during production by an infected or colonized human, not by a pig. As they say:

…the presence of MRSA in meats may pose a potential threat of infection to individuals who handle the food. … (G)reat attention needs to be taken to prevent the introduction of MRSA from human carriers onto the meats they handle and thereby spreading the pathogen.

As we’ve discussed before, the primary danger from MRSA in meat is not that people will take the bug in by mouth (though that is a danger, since S. aureus because of its toxin production can cause severe foodborne illness — and these researchers found, overall, an S. aureus contamination rate of 46% of their pork samples and 20% of their beef samples). Rather, the danger is that people handling the raw meat will be careless in preparing it, and will colonize themselves by touching the meat and then touching their own noses or mucous membranes, leading to a possible future infection. As reader Rhoda pointed out in a comment last week, people could also infect themselves directly, by getting MRSA-laden juice or blood into an abrasion or cut.

So: Be careful in the kitchen, keep meat separate from other foods, wash cutting boards and knives, and (say it with me, now) wash your hands, wash your hands, wash your hands.

The cite for the new paper: Pu, S. et al. Isolation and Characterization of Methicillin-Resistant Staphylococcus aureus from Louisiana Retail Meats. Appl. Environ. Microbiol. doi:10.1128/AEM.01110-08. Epub ahead of print 31 Oct 08.

Housekeeping note: This is the 16th post I’ve written on MRSA in food animals and/or meat. Providing all the links to the previous posts is starting to obstruct the new news. So if you are looking for all those past posts, go to the labels at the end of this post, below the time-stamp, and click on “food.” You should get something that looks like this.

Final report from ICAAC-IDSA 08 (news from ICAAC, 3)

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The ICAAC-IDSA (48th Interscience Conference on Antimicrobial Agents and Chemotherapy and 46th annual meeting of the Infectious Diseases Society of America) meeting ended a week ago, and I’m still thrashing my way through the thousands of abstracts.

Here’s my final, highly unscientific selection of papers that caught my eye:

* Evidence that the community-strain clone USA300 is a formidable pathogen: It first appeared in the San Francisco jail in 2001. By last year, it had become the sole MRSA strain found in the jail — it crowded out all others. (P. Tattevin, abstract C2-225)
* Another paper from the same UCSF research group finds that the emergence of USA300 has caused a dramatic increase in bloodstream infections, most of which are diagnosed in the ER, not after patients are admitted to the hospital. (B. Diep, abstract C2-226)
* And the CDC finds that USA300 is picking up additional resistance factors, to clindamycin, tetracycline and mupirocin, the active ingredient in the decolonization ointment Bactroban. (L. McDougal, abstract C1-166)
* An example of the complexity of “search and destroy,” the active surveillance and testing program that seeks to identify colonized patients before they transmit the bug to others in a health care institution: Patients spread the bug within hours, often before test results judging them positive have been returned from the lab. (S. Chang, abstract K-3379b)
* In addition to the report from Spain I posted on during the meeting, there is a report of emerging linezolid resistance in France. (F. Doucet-Populaire, abstract C1-188)
* And in addition to the abundant new news about MRSA in pork, and “pork-MRSA” or ST 398, in humans, over the past few days, there were reports of MRSA in milk in Brazil (W. Gebreyes, abstract C2-1829) and Turkey (S. Turkyilmaz, abstract C2-1832), and beef and chicken in Korea (YJ Kim, abstract C2-1831), as well as ST 398 itself acquiring resistance to additional drugs. (Kehrenberg, abstract C1-171)
* Echoing many earlier findings that MRSA seems most common among the poor, the poorly housed and the incarcerated, BR Makos of the University of Texas found that children are more likely to be diagnosed with the bug if they are indigent, or from the South (which I imagine is a proxy for lower socio-economic status, since the South is a more rural, more poor region). (abstract G2-1314)
* And finally, to the long list of objects (ER curtains, stethoscopes) that harbor MRSA, here are more: The ultrasound probes in emergency rooms (B. Wessman, abstract K-3377). Also: Dentures. (Ick.) (D. Ready, abstract K-3354)

TV stations find MRSA in retail pork in Pacific Northwest

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In the comments, Coilin Nunan of the UK’s Soil Association (which published the wonderful 2007 report MRSA in Farm Animals and Meat report) calls attention to a report that I also spotted over the weekend.

A network of TV stations in Washington, Idaho, Oregon and California did a joint report in which they bought 97 packages of ground pork or pork cutlets and sent them to a laboratory for testing. The lab found that three of the packages, all ground pork, contained MRSA.

I believe this is the first time anyone has found (or, perhaps, looked for) MRSA in retail pork in the US. You’ll remember that MRSA ST 398 has been found in meat in Canada and Europe, and in hospital patients in Scotland and the Netherlands, and in pigs in Iowa; and MSSA ST 398 in humans in New York City.

There are some important unanswered questions about this report:

  • We aren’t told the strain. If it’s ST 398, that would be information on the spread of ST 398 in the US. If it’s USA300, on the other hand, it could be contamination from an infected or colonized human, perhaps someone in the preparation chain.
  • We aren’t told the provenance of the pork. Was it bought from a variety of markets, or one chain of supermarkets that might have one regional supplier? Was it organic v. conventional? Small-farm versus feedlot?
  • We can’t draw any broad conclusions from this. I am a poor biostatistician, but to me, this is purely a convenience sample. (If anyone disagrees with me, please weigh in.) In other words, it’s one data point. It says: There is MRSA in these packages of pork — which is an important piece of information — but it doesn’t say: 3% of all US pork contains MRSA.

Also, while the written version of the report that I linked above isn’t bad, overall, it contains one significant error. It says:

This drug-resistant bacteria is already responsible for more deaths in the US than AIDS. What makes MRSA so potentially dangerous is the bacteria can cause sickness just by touching it.

Well, not exactly. The concern with MRSA in meat is that, if you handle it without strict cleanliness, you might become colonized with the bacteria. That is not at all the same as developing a MRSA infection, much less the invasive MRSA the first sentence of that quote refers to. And yes, colonization can lead to infection. But to say that touching MRSA-contaminated meat will inevitably cause an invasive MRSA infection is alarmist.

I’m assuming the stations undertook this because it is sweeps month. (For those who have so far been spared the internals of TV news, “sweeps” are months — usually February, May, July and November — when stations’ audiences are measured to determine market rank and advertising rates. Because it is in the stations’ interest to attract as much audience as possible during those months, sweeps is usually when news stations run big investigative projects.) Interesting that they chose this topic. I think we can take this as an indicator — again, just one data point, but an interesting one — of emerging US concern over MRSA in meat.

Microbes in US meat, but no MRSA

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The ICAAC-IDSA meeting has ended, but there are still many abstracts that I have not been through. While I pore over them, though, an interesting paper has just been published that somewhat contradicts earlier research on the presence of MRSA in meat. (Earlier posts are here, here, here, here, here, here, here and here.)

The researchers, from the Warren Alpert Medical School of Brown University and Rhode Island Hospital, bought ground beef, boneless chicken breasts and pork chops from 10 stores in and around Providence. Two stores offered both conventional and “natural” choices, so they bought both, giving them 36 (=[10+2]x3) samples all told. They cultured for MRSA, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase producing Gram-negative bacteria and E. coli 0157:H7.

And they found… almost nothing. Only one samples grew a resistant microbe, the ESBL Gram-negative Serratia fonticola. A secnd level of testing, however, uncovered four samples carrying S. aureus — but all methicillin-sensitive, not MRSA.

So are we in the clear? Not necessarily. It is, as they say themselves, as small study, in which only a third of the samples were pork, though pigs are the animals most associated with MRSA via the strain ST398. And the presence of S. fonticola is troubling, because it not only causes disease directly (in animals and in humans), but also harbors a plasmid that can transfer resistance to other bacterial strains.

Nevertheless, it is a comforting reminder that, though MRSA has been found in meat, it has not been found everywhere. (Or at least, not in Providence.) Still, we shouldn’t let our personal vigilance lapse. The hypothetical danger from MRSA in meat is not that we’ll swallow it, but rather that we’ll be colonized if we handle the raw meat without being careful enough about kitchen hygiene. So keep raw meat away from other food, wash your cutting boards and counters, and (say it with me, now), wash your hands, wash your hands, wash your hands.

The cite is: Philip A. Chan, Sarah E. Wakeman, Adele Angelone and Leonard A. Mermel, Investigation of multi-drug resistant microbes in retail meats. Journal of Food, Agriculture & Environment, Vol.6 (3&4), July-October 2008.