A newly-discovered gene that gives bacteria the ability to resist one of our last-resort antibiotics has been found in people and ground beef in Canada. Public health officials are once again raising the alarm. We asked microbiologist Jason Tetro about the gene, if there is any cause for concern and what can we do about it.
Is this new superbug gene, MCR-1, really as scary as it sounds?
On its own, it's just another mechanism of antibiotic resistance. In studies from Europe late last year, the bacteria containing the gene were still susceptible to other antibiotics. But if bacteria acquire MCR-1 and other antimicrobial resistance genes, then antibiotics could be rendered useless.
If I eat bacteria with this gene, will I get sick?
Not necessarily. You typically need to ingest thousands if not hundreds of thousands of bacteria to cause infection. If you don't, the bacteria will most likely flow through you and back out into the environment. There's also the possibility that the bacterium with the gene will just die in your gut anyway.
What if I get sick with another infection?
The MCR-1 gene only protects the bacterium that has it. If other species are causing infection and don't carry this gene, they will be sensitive to colistins (last-resort antibiotics). Most likely, you'll be given another antibiotic to kill that infection.
Where has it been found in Canada?
The gene was originally found in China and has been confirmed in a handful of other countries around the world. At the moment all we know about Canada is the gene has been found in humans and meat products in Ontario. It may be in other regions of the country but, as of yet, no data has been provided. There's a paper soon to be released by the Public Health Agency of Canada that may fill in the blanks.
Why is there such a lag between the time the Canadian samples were collected – in 2010 – and the public learning that they're in the food chain?
It's simple: no one was looking for it until recently. Antibiotic resistance is occurring everywhere – it's even in you – and it happens in a variety of ways. We knew back in 2010 about resistance to colistin but it was believed to be a specialized mechanism limited to one bacterial species – Acinetobacter baumannii. When the resistance was found in other bacteria in China, the researchers went looking for the gene and found MCR-1. No one knew if this was a new discovery or if we had simply found something lurking in many areas of the world. It turns out the latter is the case.
How can we be sure the meat we're buying is free of superbugs and of the drugs that contribute to the spread or antibiotic-resistant bacteria?
As I mentioned earlier, antibiotic resistance is everywhere and will be found in a variety of foods, regardless of whether the animals are fed antibiotics. What is important is to ensure the number of resistant bacteria only makes up a small population of the total bacteria found in animals. This means not providing antibiotics as they can shift the population towards higher numbers of resistant species. This is why having a ban on antibiotics in agriculture is important. As for the consumer, an increasing number of stores are selling meat from animals raised without antibiotics. The more we buy these types of meat, the more pressure will be put on agriculture to do away with unnecessary use of antibiotics voluntarily.
What is aiding the spread of MCR-1?
It's hard to tell at the moment. Right now, researchers are conducting evolutionary analyses to find a common ancestor. When we have that, we'll know how it spreads. If I was asked to guess, I would say migratory birds are the culprit. However, this is just a guess as there is no concrete data to support this hypothesis.
Is there anything that can be done to stop it?
There's little we can do other than limit the use of colistins from agriculture. Although this won't stop the gene from being produced or spread, it will help to increase the diversity of the overall microbial population in animals. This may allow for an ecological shift that could see these resistant species kept at very low levels incapable of causing infection, or perhaps taken out altogether, making the microbes, and the genes with them, disappear. As for humans, the best way to prevent the spread is to not become infected. For that, good old-fashioned hygiene and proper cooking of meats are the best options.