The resistance gene, called mcr-1, was first found last month in China in pigs, retail meat and human infections.
The latest discovery, by the Animal Plant Health Agency, also found mcr-1 in 10 human salmonella infections and in salmonella from a single imported sample of poultry meat.
Bacteria containing mcr-1, however, can still be treated with other antibiotics.
Scientists have claimed the resistance gene has spread from farm animals to humans because the antibiotic is used much more widely in veterinary medicine than it is in human medicine. They suggest antibiotic usage in livestock raises the potential nightmare scenario of antibiotics ultimately becoming useless to humans.
FOI request
A Freedom of Information request submitted by the Alliance to Save Our Antibiotics has established that 837kg of colistin was sold for use in British farm animals in 2014, compared with 300kg per year in human medicine.
Europe-wide, the amount used in farm animals – 545t – was more than 500 times higher than the amount used in humans (about 1t), with use in farm animals in Spain (177t), Italy (133t), Germany (124t) and France (50t) being particularly high.
Cóilín Nunan, scientific adviser to the alliance, called for the ban of “routine preventative use in farming of colistin, and all antibiotics important in human medicine”.
He said: “Despite scientists saying that resistance to this last-resort antibiotic is likely to be spreading from farm animals to humans, it still remains completely legal in the UK and in most EU countries to routinely feed colistin to large groups of intensively farmed animals, even when no disease has been diagnosed in any of the animals.
“We need the government, the European Commission and regulatory bodies like the Veterinary Medicines Directorate to respond urgently.”
Direct threat
Earlier this month, the government-commissioned a report that the use of antibiotics in agriculture posed a direct threat to human health.
The Review on Antimicrobial Resistance warned antibiotic-resistant bacteria could potentially be passed on by animals to humans through direct contact, through meat preparation, or by indirect contact as a result of animal excretion.
The Department for Environment Food & Rural Affairs (DEFRA) said that compared to other countries in Europe, colistin usage in animals in the UK is very low – making up less than 0.2% of UK antibiotic use in livestock.
A DEFRA spokesperson said: “Public Health England has said the risk to human health is very low, and the Food Standards Agency has said the risk from eating thoroughly cooked pork is also very low.”
“We are enhancing our surveillance for colistin resistance, and veterinary prescribers have voluntarily updated prescribing guidelines to restrict use of colistin in animals.”