05 June 2008

MRSA in the food chain?

Behind the growing number of findings of MRSA in food animals and the humans who work with them — in the Netherlands, Canada and now in the US — there lurks a persistent concern that the meat of those animals could be a vector for MRSA transmission. Dr. J Scott Weese of the Ontario Veterinary College raised the possibility in a presentation I reported on at the International Conference on Emerging Infectious Diseases, and Dutch researchers raised it in a paper last year as well.

Until now, though, it has been a hypothetical concern, since the humans found with pig-associated MRSA (both the already-recognized community and hospital strains and the emerging ST 398 strain) have all been animal workers.

So much for hypothesis. The London newspaper The Independent is reporting that the ST 398 strain has sickened three patients in Scotland who have no connection to animal raising or slaughtering, suggesting their infections came from contact with raw meat.
All three patients, who were being treated in at least two different Scottish hospitals, recovered. Confirming the cases, Dr Giles Edwards, director of the Scottish MRSA Reference Laboratory, said: "A lot of the patients who got this infection in Holland and Canada have been people who work with animals, such as farmers and vets. But none of the three individuals in Scotland have been in contact with animals, not that we could find." (Byline: Martin Hickman)
The bug has not currently been found in pigs raised in England, but about two-thirds of pork sold in the UK is actually imported from the Netherlands. So the Soil Association (the British farming lobby) has asked the government to begin testing imported pork for MRSA strains. The British Food Standards Agency disagrees, however, telling the Independent it does not "see serious food safety issues."

Which is strikingly close to what CDC Director Dr. Julie Gerberding said in February when asked by the House Committee on Agriculture about the Dutch and Canadian reports:
... although the finding of MRSA in retail meats suggests a possible role for foodborne transmission, if such transmission occurs, it likely accounts for a very small proportion of human infections in the United States. (Letter .pdf archived here on the site of the National Pork Producers Council.)

UPDATE: The Soil Association's statement, with some good additional references (including to a newspaper report by the Sunday Post two days before the Independent's) is here. More to come on this, I think.

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