‘Superbug’ gene alarms Canada health officials
A gene that makes bacteria resistant to a strong antibiotics — first reported in China — has made its way to Canada, according to published reports.
The gene is called MCR-1, which produces an enzyme that makes bacteria invincible to colistin, a toxic antibiotic used when all others have failed, the Toronto Star reported.
MCR-1 was initially reported in November by Chinese scientists, who published a paper in The Lancet, an international medical journal.
“The emergence of MCR-1 heralds the breach of the last group of antibiotics, polymyxins, by plasmid-mediated resistance,” the Lancet report said. “Although currently confined to China, MCR-1 is likely to emulate other global resistance mechanisms such as NDM-1. Our findings emphasise the urgent need for coordinated global action in the fight against pan-drugresistant Gram-negative bacteria.”
Researchers in China found 260 samples of E. coli with the MCR-1 gene on meat, hospital patients and farm animals.
E. coli, or Escherichia coli, is a germ (bacterium) found in the digestive tracts of humans and animals. A person can get an E. coli infection by coming into contact with human or animal feces.
The researchers found E. coli with MCR-1 on 21 per cent of slaughterhouse pigs and 15 per cent of raw chicken and pork. Sixteen hospital patients were found to have had MCR-1 infections.
“The effect on human health by mobile colistin resistance cannot be underestimated,” the researchers said.
A key finding was that MCR-1 is located on a plasmid, a freefloating piece of DNA that bacteria can share.
“It’s clearly the biggest story to come out (in 2015),” said Lance Price, an environmental health professor at George Washington University, told the Star. “There have been horrible things all year but this is the most disturbing.”
About a dozen other countries have since found the MCR1 gene, the Star reported, including Canada, which launched an investigation in December.
The Canadian results have not been published, but a case report was submitted to the Lancet, Dr Michael Mulvey, chief of antimicrobial resistance with the Public Health Agency of Canada in Winnipeg, told the Star.
The gene was found in three different samples of E. coli, all previously collected for research projects: one from a 62-year-old patient in Ottawa and two from ground beef in Ontario. The Ottawa patient likely got the bug in Egypt, where she lived for several years, according to Dr. Baldwin Toye.
The beef samples were discovered nearly a year apart in different locations in Ontario, a butcher shop and a grocery chain, Mulvey said. They were collected in 2010, before the samples from China, which were gathered between 2011 and 2014, the Star reported.
Colistin belongs to a group of antibiotics called polymyxins. It was discovered in the late 1940s but its use was discontinued because of its highly toxic side effects.
“We’ve sort of run out of our good drugs,” Price said. “So out of desperation … we have to revive this old drug because it’s all we have left.”
Colistin is rarely used in human medicine because doctors want to preserve its effectiveness. But polymyxins are given to livestock to prevent infections, particularly in China.
Colistin isn’t used in agriculture in Canada, but polymyxin B, a similar compound, is, the Star reported.
Timothy Walsh, a microbiologist with Cardiff University who co-authored the initial Lancet paper, said the Chinese government is taking MCR1 seriously and he expects it will ban colistin in agricultural use.
“Any antibiotic class used for humans should never be used for animals (unless they’re sick),” he told the Star.