The superbug MRSA has been found in a piglet in Northern Ireland - the first case of its kind in the UK.
The find has prompted calls for the Government to take action against overuse of antibiotics on farms and carry out a full MRSA survey of the pig industry.
The piglet was one of a group of five postweaning animals examined by the Omagh disease surveillance laboratory of the Agri-Food and Biosciences Institute in May.
The animals had had a history of pneumonia and wasting, and the herd had shown 10% mortality over the previous two to three months.
A report in the veterinary record said MRSA – which is resistant to the antibiotic methicillin – was first identified in livestock in The Netherlands in 2003 and was associated with pigs, pig farmers and cattle.
It has since become widespread in intensively farmed pigs, poultry and veal calves in many European countries and North America, but this is the first time a case has been reported in pigs in the UK.
Alison Craig, campaign manager for the Alliance To Save Our Antibiotics, said: "The finding of MRSA in a UK pig has to kick-start the Government into finally taking action against the overuse of antibiotics in farming."
The group said LA-MRSA (livestock-associated MRSA) can spread to humans and cause serious infections including blood poisoning, pneumonia and heart and bone infections. People directly in contact with affected farm animals, including farmers and vets, are most at risk.
Derek Butler, chairman of MRSA Action UK, said: "We are sitting on a timebomb waiting to explode. Sooner or later bacteria will transfer from animals to humans, causing infections."
The Department of Agriculture said: "DARD is aware that the first case of Livestock Associated MRSA (LA-MRSA) in the north was identified several weeks ago in a 6-8 week old piglet. This case poses no risk to the general public and is different from the MRSA strain that can be found in healthcare.
"LA-MRSA presents a low occupational risk for those working in close contact with infected livestock and is not a notifiable disease. Meat from LA-MRSA affected animals is perfectly safe to eat provided good hygiene and thorough cooking practices are observed. DARD is providing advice and assistance to those on the farm in question.'
LA-MRSA stands for Livestock-Associated Methicillin Resistant Staphylococcus aureus. There are no known cases of people contracting MRSA from eating meat. LA-MRSA was first found in pigs in the Netherlands in 2004, and has since become widespread in intensively farmed pigs, poultry and veal calves in many European countries. A Dutch study published last month found that LA-MRSA was spreading to people without direct contact with farm animals.