Press conference comments: study leader Dr. Ron Read

On the study background

This study was done in response to concerns that antibiotic resistance that arises in an agricultural setting, in response to uses of antibiotics in agriculture, might somehow be transmitted to humans.

As an infectious disease physician in human medicine, my concern would be that if we're starting to see bacteria that would be difficult to treat because of resistance that is arising from an agricultural setting, then that's important to know.

This was a theoretical concern. And because of the issues that had occurred in Europe, the beef industry here was interested in knowing whether they were in any way contributing to this concern. There was just no data out there. We undertook the study to act as a baseline to see whether it was an issue and what the specific concerns were.

On the methodology

We looked at animals within commercial feedlots, and asked the question: Is resistance occurring in that setting? We looked specifically at people who worked in feedlot environments to determine whether there was any movement of organisms from cattle to humans who have direct daily contact with those animals. And we did experiments in model feedlots to look at the roles of specific individual antibiotics to see whether they result in resistance or influence the movement of resistance around the feedlot.

The magnitude of the study was such that the number of isolates we ended up looking at was huge. We had about 100,000 bacterial isolates in our collection.

We used sampling and susceptibility testing methodologies that were very time consuming, but we used what were considered the gold standard - the methodologies upon which other methodologies were compared.

On the results

Most of the resistance concerns that we had going into the study turned out not to be concerns. That was reassuring. The one thing that did come out was resistance to broad-spectrum cephalosporin drugs, by the so-called AmpC mechanism, which we really weren't expecting to find. The industry will now need to decide how it's going to respond to that finding and what can be done to mitigate it.

Our major recommendation at this point is to support the work of CIPARS {Canadian Integrated Program for Antimicrobial Resistance Surveillance}. CIPARS is a federally mandated surveillance program that looks at resistance issues in both humans and in agriculture. I think the most important thing we can do is to continue to keep an eye on this phenomenon.

On transfer potential

There are a number of possible ways the organism {E. coli with resistance to cephalosporins} could move. The one we studied was direct transmission. Somebody who works with cattle on a daily basis - is there any evidence that they acquire it?

Remember, feedlots have conditions where there's quite a lot of manure around, and that's where the organisms are present. People are working in that environment on a daily basis. But we did not find any movement, at all, of the organism into the people that are working with the cattle.

A second possibility is groundwater. We didn't study that specifically, so I can't make any comment about that. But we don't have any reason to suspect that is a very likely route, because we're not seeing the movement of run-of-the-mill E. coli into the water supply.

Finally, the food chain contamination of carcasses and meat that makes its way into retail stores is another possibility. We did not specifically study that, but there are ongoing surveillance processes and regulations in place to evaluate that.

What I can say is that people who work on a daily basis with this organism have not acquired illness from it and do not have any evidence of carriage of it. Also, since the time that we did our sampling, we are not seeing, in the clinical human environment, people coming in with infective conditions involving this organism.