Study finds Enterococcus bacteria resistance in people not related to antibiotic use in cattle

Dr. Tim McAllister, a principal research scientist at the Agriculture and Agri‑Food Canada Research and Development Centre in Lethbridge, Alberta, says that, he and his team have found nothing to indicate that antimicrobial resistance (AMR) in beef cattle is being transmitted to humans.

The recent study was published in the academic journal Scientific Reports this week.

“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.”

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Dr. McAllister is among close to two dozen scientists at five different federal departments and agencies, Alberta Agriculture and Forestry and the University of Calgary 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 five‑year Genomics Research and Development Initiative ‑AMR project, launched in 2016, is a major component of the Federal Action Plan on Antimicrobial Resistance and Use in Canada. The project also required coordination with feedlot veterinarians, commercial feedlot operators and was partially funded by the Beef Cattle Research Council Cluster.

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.”

Using the highly detailed molecular data that can be acquired through whole genome sequencing, Dr. McAllister’s team has determined that the Enterococcus bacteria found in cattle and the Enterococcus that poses a serious threat to human health 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 Genomics Research and Development Initiative and the Beef Cattle Research Council has yet to find any evidence that 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.”

Read the study online at nature.com.

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