Federal researchers: antibiotic use in cattle not related to antimicrobial resistance in humans

 

- Ottawa, Ontario

Research funded through the Government of Canada's Genomics Research and Development Initiative (GRDI) is delivering what amounts to good news about antimicrobial resistance (AMR) for both beef producers and beef consumers. Dr. Tim McAllister, a Principal Research Scientist at the Agriculture and Agri‑Food Canada Research and Development Centre in Lethbridge, Alberta, says that, so far, he and his team have found nothing to indicate that antimicrobial resistance in beef cattle is being transmitted to humans.

A shared risk

"Antimicrobial resistance is a serious concern for both animal and human health, and part of addressing those concerns is understanding whether there are any linkages between the two," says Dr. McAllister. "So, at least as far as beef cattle are concerned, this is a significant finding."

Dr. McAllister is among close to two dozen scientists at 5 different federal departments and agencies involved in a series of interlocking research projects aimed at understanding whether antibiotic use in the beef, pork and poultry industries is increasing the risk of AMR in humans—and if so, what steps can be taken to reduce the risk. The 5‑year GRDI‑AMR project, launched in 2016, is a major component of the Federal Action Plan on Antimicrobial Resistance and Use in Canada.

AMR knows no borders

"Antimicrobial resistance is a serious concern for both animal and human health, and part of addressing those concerns is understanding whether there are any linkages between the two. So, at least as far as beef cattle are concerned, this is a significant finding."

Focusing on the beef industry, Dr. McAllister collaborates with researchers in other departments in taking a "One Health" approach to the issue. "Basically, that's just recognizing that there are no borders when it comes to AMR," says Dr. McAllister. "Bacteria with AMR can be found in humans, in animals, and in the environment, and they may spread from one to the other. That's why, in our research, we're looking at bacteria from people being treated for infections in hospitals, from cattle in feedlots, from waterways, from processing plants, sewage plants and elsewhere to see where and what type of AMR exists, and whether we can make any connections from one to the other."

GRDI support key to progress

Dr. McAllister is quick to credit the GRDI for making the research possible. "We now have access to technologies such as whole genome sequencing (WGS) that enable us to get so much more data from the bacteria we're looking at, including identifying the individual genes that provide the bacteria with AMR," says Dr. McAllister. "GRDI has also been great for collaboration across departments. We're applying research tools in our program that would not have been possible without the input of the Public Health Agency of Canada, the Canadian Food Inspection Agency, Health Canada and the National Research Council."

Some surprising findings

"We have tried really hard to find the smoking gun—that link of AMR and beef to humans—and we have not."

Using the highly detailed molecular data that can be acquired through WGS, Dr. McAllister's team has determined that the Enterococcus bacteria found in cattle and the Enterococcus that poses a serious threat to human health—long thought to be the same—are actually entirely different species of bacteria. "We have also discovered that the genes responsible for AMR in the Enterococcus bacteria in humans are associated with antibiotics that are never used in cattle—in other words, it is becoming clear that AMR in cattle is the result of antibiotics used in cattle, and AMR in Enterococcus bacteria found in humans is the result of antibiotics used in humans."

At the same time, he cautions that you can never say never. "There are billions of cells out there and they are masters of adaptation, so there's always a chance," says Dr. McAllister. "We have tried really hard to find the smoking gun—that link of AMR and beef to humans—and we have not. Still, we can't rule out that there could be a very lucky shot some time in the future. The chances of that happening are very, very low, but they're not zero."

Industry welcomes "important step forward"

Genomics research funded through the GRDI has yet to find any evidence antimicrobial resistance in beef cattle is being transmitted to humans.

At the Beef Cattle Research Council, Science Director Dr. Reynold Bergen says Dr. McAllister's research represents an important contribution to the development of science‑based policy and regulations on the use of antimicrobials in food production.

"AMR is a major concern for people and for the beef industry, and something the industry has been researching for more than 20 years," says Dr. Bergen. "We need antimicrobials to continue to work in people when they get sick, and we need them to work in cattle when they get sick. Dr. McAllister's research is an important step forward—with no evidence that AMR is being transferred from cattle to people, or vice versa, we can bring new focus to our research, based on the understanding that, although we must continue to use antimicrobials responsibly in both human medicine and cattle production, AMR in humans and AMR in cattle are separate issues."