Following an announcement from scientists in China last month that bacteria found in farmed animals and humans had gained resistance to medicine’s last resort treatments, researchers have discovered that the bug has spread much more widely than previously thought, including to the UK.

First detected in a strain of E.Coli from a pig farm by a researcher at one of China’s agricultural universities, a gene (called mcr-1) can be spread easily between bacteria and confers resistance to the polymyxin class of antibiotics. This class includes colistin, the drug used when all others have failed.

The discovery means that disease-causing bacteria (which cover a range from E.Coli to bubonic plague) could become ‘pan-resistant’ - literally untreatable with modern methods. Resistant bacteria were subsequently found in a number of hospital patients in China.

Reporting their findings in medical journal the Lancet last month,  the researchers said that the overuse of colistin in animal agriculture was the most likely cause of the spread in resistance.  They suggested that, as well as being present in China, the bacteria could have spread to Laos and Malaysia.

Now though, new findings published since the beginning of the month suggest the resistant gene has already spread more widely than the scientists who detected it could have guessed. Earlier in December, a Danish researcher found the strain in samples taken from poultry meat imported into the country from Germany, and from one hospital patient in Denmark. The bacteria also carried genes conferring resistance to numerous other treatments.

Since then, resistant bacteria has been found in France, the Netherlands, Portugal and in several Asian and African countries.

Mcr-1 detected in Britain

This week it was revealed that the resistant gene had been detected in infectious bacteria samples from the UK. Government scientists have found mcr-1 in E. coli from pigs (and resistant salmonella from one imported sample of poultry meat) and in several human E. coli and salmonella infections in England and Wales. The earliest detected sample was a case of salmonella from 2012. As was the case with the Danish samples, the E.Coli from human infections was also resistant to other antibiotics.

Though it is uncertain where resistance to Colistin first developed, China is a possible candidate, due to the high usage of the drug there. As the researchers who discovered the resistant mcr-1 gene suggested, scientists believe that 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.
 
On Tuesday, campaigners from the Alliance to Save Our Antibiotics said figures show that in Europe as a whole, the amount of colistin used in farm animals (545 tonnes) is more than 500 times higher than the amount used in humans (about 1 tonne), with use in farm animals in Spain (177 tonnes), Italy (133 tonnes), Germany (124 tonnes) and France (50 tonnes) being particularly high.
 
Cóilín Nunan, Scientific Adviser to the Alliance, said  the discovery of mcr-1 and its apparently rapid spread could signify a major step towards completely untreatable infections. He commented, “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. The routine preventative use in farming of colistin, and all antibiotics important in human medicine, needs to be banned immediately.”
 
The mcr-1 gene is found on mobile pieces of DNA which means it can jump from farm-animal bacteria into bacteria causing human infections. This also explains why it is spreading so widely and is already being found in many different strains of E. coli, salmonella and Klebsiella pneumoniae.
 
Recently 20 senior representatives from health and medical organisations co-signed a letter, published in the Times, calling on the UK Government and European Commission to put an end to routine, purely preventative antibiotic use in groups of healthy animals. The letter follows a Veterinary Medicines Directorate’s report which revealed that the total UK veterinary sales in 2014 of antibiotics classified as “critically important in human medicine” increased by 3% to a new record high.
 
UK veterinary and farming sectors have agreed to temporarily limit the use of colistin, but no action has been taken by regulators to stop routine mass medication with the antibiotic.