Monday 5 December 2016

'Superbug' MRSA found in sausages and minced pork sold in supermarkets

Tim Moynihan

Published 18/06/2015 | 20:08

Sausages on the barbecue grill
Sausages on the barbecue grill

The "superbug" MRSA has been found in sausages and minced pork obtained from supermarkets in the UK, according to a report published today.

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However, researchers stressed it did not pose a significant immediate risk to the public and said sensible food precautions and good hygiene should prevent its spread.

In February, a team of researchers funded primarily by the Medical Research Council (MRC) bought and analysed a total of 103 (52 pork and 51 chicken) pre-packaged fresh meat products, labelled as being of UK farm origin, from supermarkets in five different locations across England.

All of the meat products were frozen at minus 20C (minus 4F) and sent to the Department of Veterinary Medicine at the University of Cambridge for testing. After thawing, researchers disinfected the exterior packaging before removing the meat, then tested a 10g sample from each packet, and screened for MRSA.

Two of the pork samples - one from sausages, one from minced pork - tested positive for MRSA; the sausage sample contained two strains of the bacteria.

An analysis of the genetic make-up of the bacteria, in collaboration with the Wellcome Trust Sanger Institute, confirmed the presence of antibiotic resistant genes.

The analysis showed the bacteria belonged to a type of MRSA known as LA-MRSA CC398, which has emerged over the last few years in continental Europe, particularly in pigs and poultry, but was not previously believed to be widely distributed in the UK.

In many countries, LA-MRSA CC398 represents an occupational risk for those in close contact with livestock, particularly pigs and veal calves.

Humans in contact with pigs (farm workers, abattoir workers and veterinarians, for example) have significantly higher rates of the bacteria in their nasal carriage, according to studies.

Other research has revealed an association between clinical disease resulting from LA-MRSA CC398 infection and recent contact with pigs or pig farms.

As with other MRSA, this type may be responsible for serious illness following wound or surgery site infections, though many people will carry MRSA on their skin or in their noses without showing signs of disease.

The researchers stressed that adequate cooking (heating above 71C/160F) and hygienic precautions during food preparation should minimise the likelihood of transmission to humans via contaminated pork.

However, they argue that the discovery of MRSA in pork identifies a potential way the bacteria can spread from farms to the wider population.

While human contamination of carcasses or meat products in the abattoir or meat packing plant may occur, there is good evidence that these isolates are of animal origin - possibly through the use of antibiotics to treat or control infection in livestock.

As the tests use a highly sensitive method of detection of bacterial contamination, the numbers of MRSA bacteria present may be low.

Dr Des Walsh, head of infections and immunity at the MRC, said: "Studies like this are crucial not just to reveal concerns to human health through contaminated livestock, but to show resistance to antibiotics is a problem growing far beyond just humans.

"To win the fight against antimicrobial resistance, we need an all-hands-on deck approach, and that's why we've teamed up with leading experts in biological, social and other sciences in a joint initiative designed to find new solutions, fast."

The research was funded by the Medical Research Council, with additional support from the Alliance To Save Our Antibiotics. The results are published in the online journal Eurosurveillance.

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