Two studies, both published yesterday, have found the superbug MRSA in pork on retail sale in the UK. A study commissioned by the Alliance to Save Our Antibiotics tested 52 samples of British pork from English supermarkets and two of them contained MRSA. This is the first time livestock-associated MRSA has been found on pork in the UK.

The other study, part of a wider investigation by the Guardian newspaper into the human health implications of livestock-associated MRSA, set out in this short film, tested 100 samples of pork products, 74 from Denmark, one from Ireland and 25 from the UK. Nine of these contained MRSA, though in this study all the UK samples were free from contamination.

Additional testing is needed to provide a more comprehensive picture of the level of MRSA in UK farm animals and food. But at the moment there are no signs that the Government will go back on its longstanding refusal to carry out systematic testing of farm animals or meat.

Livestock-associated MRSA first emerged in Dutch pigs about a decade ago and has spread from there to most European countries, some of which now have levels in pigs far higher than in Denmark, and to other farm animals. It has separately emerged as a significant problem in Canada and North America and also in China and other parts of Asia.

The Guardian’s film illustrates in graphic detail the impact MRSA caught from pigs can have. They interviewed a number of workers from Danish pig farms who had developed serious MRSA skin infections, which in one case had still not cleared up, despite several courses of antibiotics.

How concerned should we be? Comments from the Food Standards Agency and other officials claim that MRSA in meat poses a very low risk as thorough cooking will of course kill the bacteria. But as we know from the continuing high incidence of campylobacter food poisoning, bacteria have a number of ways of getting round our defences. And that they actually do that is borne out by the growing number of cases, a few from the UK, more in other countries, where many of those infected with this particular type of MRSA have had no direct contact with farms or farm animals.

The most likely cause of colonisation would be if you involuntarily rubbed your nose while handling raw pork. Staphylococcus aureus, the type of bacteria that cause MRSA infections, live on the skin and especially in our noses, as well as in our intestines and elsewhere. They can live there harmlessly for long periods but a tiny scratch or wound can quickly become infected with them. Interestingly Staph. aureus never colonise the skin of about a third of the population. As yet no one knows why that is, but should we one day completely run out of antibiotics for treating MRSA perhaps evolution will play a part in helping the human species to survive, with those not affected probably passing on this characteristic to their children.

At the present time there are still effective antibiotics to treat most cases, so it is actually less of a concern to health professionals than infections caused by tuberculosis, E. coli, gonorrhoea and some other broadly related bacteria where an increasing number of cases are resistant to the carbapenems and other antibiotics of last resort and no suitable new antibiotics are under development. But does that mean we should not be concerned, perhaps not even take any effective action, which for the last decade has essentially been the UK Government’s response?

Cóilín Nunan, Principal Scientific Adviser to the Alliance, has said: “A significant number of people have already died from (livestock-associated) MRSA infections including five in Denmark and several in Germany. LA-MRSA is evolving and more dangerous variations are emerging. Scientists are warning it could ultimately lead to a pandemic spread in humans as so many animals carry the superbug”.

Nunan, who drew evidence to the attention of the Scottish MRSA reference laboratory, which led to the first identification of LA-MRSA in the UK, has been studying the science and the emerging global trends in more detail than anyone in the UK since 2005. He’s aware that what makes some community-acquired strains of MRSA more deadly even than most hospital strains (they sometimes lead to death in just a few days) is that they can carry extra virulence genes. He says, “Virulence genes can pass from one strain of bacteria to another, just like resistance genes, and scientists in other countries have noted that ST398, the strain currently causing most LA-MRSA infections, is particularly prone to acquiring virulence genes.”

As such he believes it is only a matter of time before this happens. If we allow a large reservoir of MRSA to build up in farm animals this could turn into a very serious problem in future.

The Sustainable Food Trust is a member of the Alliance to Save Our Antibiotics and fully supports the Alliance’s call for further restrictions on the use of antibiotics on farms, as set out in more detail in their press release, as the only way to address this problem sustainably – a change which would also need farm animals to be kept in more natural ways so they rarely, if ever need treating with antibiotics.

Photograph: Dgphilli

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