New research that will be presented at this year’s European Congress of Clinical Microbiology and Infectious Diseases has found that raw dog foods contain high levels of multidrug-resistant bacteria, including some that are resistant to last-line antibiotics. The study was conducted at the University of Porto in Portugal.
The authors have concluded that potential transfer of these pathogens from dogs to humans is “an international public health risk.” The authors include Dr. Ana Raquel Freitas and colleagues from the Faculty of Pharmacy at that university.
These raw dogs foods are popular, and are offered as a “healthier” choice. One of the problems with this type of food is that dogs can be reservoirs of clinically-relevant ampicillin-resistant Enterococcus faecium, but scientists don’t know the source of this pathogen.
There have been many recalls of raw frozen dog foods in the past few years. Last year, a Salmonella Infantis outbreak that sickened dozens of people included raw chicken pet food as one of the probable sources.
The authors looked at enterococci obtained from processed (dry and wet) and non-processed (raw frozen) foods of the main brands that are available in Portugal. The food was sourced from eight supermarkets and one veterinarian clinic. Samples were obtained from September to November in 2019. The raw frozen samples were salmon, chicken, turkey, calf, deer, and duck, with a different mix of fruits and vegetables.
Samples of the food were cultured and tested with a range of antibiotics. Enterococci were identified in 41% of the samples. Fifty-three percent of the dry foods contained this pathogen. Two of 22 of the wet foods were contaminated, and 100% of the raw frozen samples were contaminated.
Across the nine raw frozen meat samples, there were 30 E. faecium and 30 E. faecalis recovered. All nine samples of the raw food carried multidrug-resistant enterococci, including those that are resistant to a wide range of antibiotics. Only one multidrug-resistant E. faecium was detected in one of the wet food samples. The dry food samples did not have any multidrug-resistant bacteria.
The authors conclude by stating: “Our study demonstrates that raw-frozen-foods for dogs carry MDR enterococci including to last-line antibiotics (linezolid) for the treatment of human infections. The close contact of pets with humans and the commercialisation of the studied brands in different EU countries pose an international public health risk if transmission of such strains occurs between dogs and humans. There is strong past and recent evidence that dogs and humans share common multidrug-resistant strains of E. faecium, and thus the potential for these strains to be transmitted to humans from dogs.”
Dr. Freitas added, “These raw-frozen foods are supposed to be consumed after being thawed and could at least be cooked, to kill these drug-resistant and other bacteria. Although these foods seem to be regulated regarding their microbiological safety by EU authorities, risk assessment of biological hazards should also include antibiotic-resistant bacteria and/or genes besides only establishing the presence of bacterial pathogens, such as Salmonella.”
