Back in 2008, we reported an association between feeding raw diets to dogs and shedding of cephalosporin-resistant bacteria in dogs (that makes me feel old… one of many things that does these days, I guess). It didn’t get too much attention at the time, since the main focus of the study was on Salmonella, the most commonly discussed concern with raw diet feeding. We also didn’t pay as much attention to those other bacteria 11 years ago.

I was speaking about antibiotic resistance at the 2019 ACVIM Forum in Phoenix AZ last week, and extended-spectrum beta-lactamase (ESBL)-producing bacteria kept coming up – not just from me, but also in lots of questions from the audience. ESBLs are enzymes that bacteria produce to break down some commonly used (and important) antibiotics, including 3rd generation cephalosporins. These bacteria also tend to acquire various other resistance genes, making some strains highly drug-resistant. ESBLs can be produced by a range of Gram negative bacteria, most notably E. coli, and these bacteria are causing more and more problems. Bacteria can also be resistant to 3rd generation cephalosporins via a different resistance mechanism that’s also of concern. Sometimes, studies focus just on ESBLs while others cover cephalosporin resistance by other mechanisms as well. Resistance by either mechanism is a problem.

One thing that got a lot of people talking at the conference was discussion of things that increase a dog’s risk of shedding ESBLs (or, more broadly, antibiotic-resistant bacteria). One risk factor is previous antibiotic treatment. That’s not surprising. The other big risk factor that’s come up in a few recent studies happens to be feeding raw diets.

  • Our study from 2008 reported dogs that ate raw meat were 15X more likely to shed cephalosporin-resistant E. coli.
  • A UK study reported an 11X higher risk of shedding 3rd generation cephalosporin-resistant E. coli by raw fed dogs. (Schmidt et al. 2015)
  • Another study from the UK reported that dogs that ate raw poultry were 48X as likely to shed ESBL E. coli compared to dogs that didn’t. (They were also 104X (!!) as likely to shed E. coli resistant to fluoroquinolones, another important drug class). (Wedley et al. 2017)
  • In a Dutch study, dogs that were fed raw meat were twice as likely to shed ESBL producing E. coli. (Baede et al. 2015)
  • The same Dutch group also looked at cats, and found that raw feeding was the only factor associated with shedding ESBL-producing bacteria, with a 32X increased risk. (Baede et al. 2017)

These results are actually not surprising.  Resistant bugs can be present in food animals, and those bugs can then contaminate the meat from those animals at slaughter or a subsequent step in the production chain. Measures are taken to reduce the risk, but whether it’s an “ultra-premium” raw diet product or meat from the local grocery store, there’s always some risk of bacterial contamination. That’s why we cook meat, and why we should always use basic hygiene practices to reduce cross-contamination and inadvertent exposure to harmful bacteria in the kitchen and elsewhere.

I won’t get into the whole raw diet discussion here but will hit on some of my highlights:

  • Raw feeding is associated with risk to the pet and owners, and should be avoided whenever possible.
  • In some situations, raw diets should never be fed to pets, including households with young kids, elderly individuals, pregnant women or immunocompromised individuals, or with animals that fit into similar risk groups.
  • High-pressure pasteurization likely reduces contaminant levels but doesn’t sterilize the food. If someone is going to feed a raw diet, they should use one of these diets but still consider the food contaminated.

More information about raw diets and how to reduce the risk when feeding a raw diet is available on the Worms & Germs Resources – Pets page.