Maryn McKenna

Journalist and Author

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.

British newspaper discovers ST398, says no UK cases – incorrect

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The UK’s Sunday Express takes note today of “pig MRSA” ST398 (full post archive here) in a story that is both somewhat alarmist and oddly incomplete, since it misses a piece of news that I told you about here last June.

The Express story raises the alarm over ST 398 in pigs in the Netherlands, colonizing farmers and causing human illnesses. There is nothing in it that we have not already discussed here many times, but it is nevertheless worth noting because it appears to be the first report on ST398 in a year in a major UK paper. (Credit for what I think is the first mention of ST398 in the Brit press goes to the Independent.)

But here’s what’s odd about the story: It says (italics mine),

A DEADLY new form of MRSA is believed to be spreading from farm animals to humans – already the bacteria has been found in hospitals abroad.
It is the first time the bug has spread in this way and experts believe excessive use of antibiotics in factory-farmed animals may be behind its development.
“Farm animal” MRSA, as it is known, can cause a raft of illnesses including skin infections, pneumonia, bone infections and endocarditis. …
The new MRSA bug, known as ST398, could reach hospitals in the UK, causing serious illness and death among vulnerable patients. (Byline Lucy Johnstone and Martyn Halle)

However as constant readers here already know, ST398 has already has been found in UK hospitals: in three unrelated patients — one adult and two newborns — in a Scottish hospital, none of whom had any relationship to pig-farming.

Credit for pushing the story of ST398 in the UK goes to the organic/sustainable farming group the Soil Association, who have aggressively monitored and lobbied for the extremely slow reveal of ST398 by the British government. As the issue now stands, the UK tested British pigs for ST398 colonization in 2008, but has not revealed the results. It has not yet tested retail meat in the UK, some of which is imported from the Netherlands, the location where the most ST398 has been found.

While that sounds like foot-dragging, it is still ahead of the US: Except for the study published in January by Tara Smith’s team at University of Iowa (paper here, my Scientific American story here), there has been no testing of pigs in the US, certainly none by government agencies.

(Hat-tip to Pat Gardiner for alerting me to the Sunday Express article.)

More on “pig MRSA” and the havoc it can do

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Folks, before I get to the SHEA abstracts, one more post on ST398 in humans, and a sad and difficult story. It is the first (to my knowledge) report of ST398 spreading into a nursing home, in the January 2009 issue of Eurosurveillance Weekly.

It was very thoroughly investigated, because it took place in the Netherlands, where by national policy there is active surveillance and testing — AKA “search and destroy” — for MRSA in health care facilities.

To me it is both an object lesson in the unpredictable spread of this newly recognized organism, and also an exploration of the deep human cost of combatting it.

The nursing home, in a town called Doorn, is described as a residence for “visually and intellectually disabled” people, and it sounds like a good place, made of 35 household-like units that hold 8 residents each, with a pretty high ration of staff to residents. One resident in one unit was an adult man (age not given) who was completely blind and significantly mentally disabled. Since 2004, he had been living with hidradenitis suppurativa, a condition of painful, recurring, weeping infections of the skin that can be caused by staph. Periodically, he was treated with a variety of antibiotics — tetracycline,erythromycin, flucloxacillin, trimethoprim/sulfamethoxazole, clindamycin, minocycline, rifampicin — but none of them seem to have made much difference to the infections. (Hidradenitis is an awful condition; there are times when the only treatment is skin grafts.)

In October 2007, the regular swabs taken of his infections suddenly showed not drug-sensitive staph, but MRSA. Confirmatory swabs showed that he was colonized with MRSA in the nose, throat and groin. After analyzing whom he might have been in contact with, the home identified 43 resident and staff at risk, swabbed them all, and found 2 other residents and 3 staff members colonized. That led to another round of swabbing, of 160 people, but no other cases of colonization were found.

So, just to recap, that is the index case, with MRSA infections and colonization in various places on his body, plus five others who were only colonized.

Sequencing/typing of the isolates found that all 6 were carrying ST398, falling into one of two spa types, t2383 and the more rare t011. None of the residents or staff had had any contact with livestock. They did have play/therapy animals at the residence — rabbits, chickens and goats — but they were checked and were all negative. The source was never found.

The five who were only colonized were given 5 days of decolonization therapy: mupirocin gel (Bactroban) in the nose and showers with chlorhexidine soap (Hibiclens). Afterward, they had to be proved negative on three successive nasal cultures; the paper does not say how far apart the cultures were. Until the third negative culture, staff had to stay home, and residents were banned from group activities. Underlining that: Physically or mentally disabled adults living in an enclosed, supportive society had to be isolated from it because they acquired this bug. Just think how difficult that must have been. The paper notes: “The outbreak caused commotion among the staff members, and they had a lot of practical questions as they were unfamiliar with MRSA and an MRSA-outbreak in particular. Furthermore, it turned out that the use of gloves, surgical masks and aprons during washing and clothing was perceived as threatening by the clients.“

The index case’s situation is even sadder. He was given a private bath and shower, and essentially restricted to there and to his private room. He had been in group day-care, but was switched to being minded by himself. His “social contacts with other residents who lived in other units was restricted to a minimum” — presumably he was not able to be fully secluded from the other members of his household. However, anyone who came into direct contact with him — for instance, to bathe and dress him — had to be on contact precautions: gloves, aprons and surgical masks. This went on for six months while his very refractory MRSA was treated with oral antibiotics and surgical incision and drainage of his abscesses; after six months, his symptoms had not resolved, but swabs of his wounds were MRSA-negative, and some of the isolation precautions were lifted.

Underlining: Someone blind and mentally disabled, presumably fairly secure in the enclosed, supportive society of the residential home, has to be restricted from his routine, from people who are probably his friends, and from all skin-to-skin contact, for half of a year.

Now, mind you: If you or I had a relative in that home, we might want them to do exactly what they did do. It is difficult to say how well the staff might have succeeded in getting mentally disabled residents to cooperate with, for instance, hand-washing.

But this is not the first case I have heard of where the cost of protecting a group from MRSA has fallen very, very hard on one individual. I am not going to argue with the Dutch policies, but in this case, I find their unintended consequences terribly sad.

“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.

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.