Canadian scientists on trail of MCR-1 gene that makes some bacteria drug-resistant

TORONTO – The discovery that a gene which turns some bacteria into antibiotic-resistant superbugs has been in Canada for at least five years has scientists wondering when it first emerged and how to stop its spread.

The MCR-1 gene makes E. coli and some other species of bacteria resistant to colistin, an antibiotic considered the drug of last resort for some diseases.

The existence of MCR-1 was first reported in November in the medical journal the Lancet after scientists identified the gene in E. coli samples taken from farm animals, meat and hospital patients in China.

What makes MCR-1 so alarming is that rather than being tethered within a chromosome, the gene is found on a circular bit of free-floating DNA called a plasmid — which can easily be swapped between bacteria, thereby allowing more micro-organisms to fend off the killing effects of antibiotics.

“It’s not only that certain strains of bacteria become resistant,” said Gerry Wright, director of the Institute for Infectious Disease Research at McMaster University in Hamilton.

“Once the genie is out of the bottle, once they start moving around, then it becomes very, very challenging to contain.”

News that a new antibiotic-resistance gene had been discovered in China — it’s since been found in several other countries — sent scientists at the Public Health Agency of Canada’s National Microbiology Laboratory on a hunt for MCR-1 in about 1,000 bacterial samples collected from hospitals and provincial labs.

The superbug gene did turn up: in E. coli from an Ottawa woman who had been treated for a likely unrelated intestinal disorder in 2011 and two E. coli samples from beef sold in Ontario in 2010, prior to the Chinese samples, which were collected in 2011 and 2014.

Dr. Matthew Gilmour, scientific director general of the Winnipeg lab, said PHAC scientists are now looking at earlier samples to try to determine how far back MCR-1 was first present in Canada.

The lab has also designed a test to detect the gene for use by hospital labs across the country, Gilmour said Tuesday.

Wright, who first heard about MCR-1 from the Lancet report, has also begun studying the gene, with the goal of finding a means to stop it from being incorporated by other bacterial strains.

“What we want to be able to do, now that we know this gene is here and it’s a potential threat to human health, we want to be able to see if we can find a molecule that blocks MCR-1’s activity,” he said. “If we can find such a molecule, then we’ll be able to combine it with colistin so you could still use that drug.”

Wright said Canadians should be concerned about the existence of MCR-1 because its emergence adds to the growing phenomenon of bacterial resistance to often life-saving antibiotics.

“It wouldn’t be such a big deal if we had a big arsenal of antibiotics, but we don’t,” he said. “There are no new antibiotics coming to market.

“So that’s the reason to be scared. This has the potential to affect us all.”

Follow @SherylUbelacker on Twitter.