Microorganisms that infect animals, such as dogs, have the potential to jump to humans and cause illness. Zoonosis is a disease that can spread from animals to humans. These diseases pose health risks, mainly that some types can become life-threatening. Now, a study warns that raw-type dog food contains high levels of multidrug-resistant bacteria, which has the potential of transmitting the bacteria between dogs and humans.
The team of researchers at the University of Porto in Portugal unveiled the dangers of raw-food-based diets for dogs, a diet that has gained immense popularity among pet owners. However, this type of dog food has been the center of debates regarding its safety. The study, which will be presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) aims to determine if raw-type dog foods play a role as vehicles for transmission of antibiotic-resistant bacteria.
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Antibiotic resistance is becoming a rampant problem across the globe. World Health Organization (WHO)’s Global Antimicrobial Surveillance System (GLASS) shows how widespread this problem is, with antibiotic resistance in about 500,000 people with suspected bacterial infections across 22 countries.
The most commonly reported resistant pathogens include Staphylococcus aureus, Streptococcus pneumoniae, Salmonella spp., Escherichia coli, and Klebsiella pneumoniae.
Enterococci are opportunistic pathogens, which means they are part of the healthy flora in the body. When the patient’s immune system becomes suppressed, these bacteria can cause infections. In dogs, they can become reservoirs for ampicillin-resistant (AmpR) Enterococcus faecium, but the source is still unclear.
In the study, the researchers studied bacteria obtained from both wet and dry processed dog food, and non-processed or raw-frozen dog foods, all of which are the major brands that are commercialized in Portugal. The study included 46 samples, including 22 wet, 15 dry, and 9 raw-frozen dog food, which were obtained from eight supermarkets and one veterinary clinic. The raw-frozen dog food usually contained calf, deer, duck. Turkey, chicken, and a combination of meat types, vegetables, and fruits.
Raw-food samples contain MDR bacteria
After culturing and testing the samples with a range of antibiotics, the team found that across nine raw-frozen samples, there were 30 E. faecium and 30 E. faecalis bacteria recovered. These nine samples also contained the multidrug-resistant enterococci, which included those that are resistant to a multitude of antibiotics. On the other hand, only one MDR-E. faecium was detected in one sample of the wet foods, while none were detected in dry dog food.
Further, the raw-type samples were resistant to antibiotics, including erythromycin, tetracycline, ampicillin, ciprofloxacin, chloramphenicol, and streptomycin. Seven of the nine samples contained enterococci resistant to the last line antibiotic linezolid, and six of the nine were resistant to gentamicin or quinupristin-dalfopristin.
“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 commercialization 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 are 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,” the authors wrote in the paper.
Over the years, studies have shown that raw-frozen dog food contains bacteria, which can be harmful to both the dogs and their owners. These bacteria may cause disease, and those that are multidrug-resistant are extremely difficult to treat.
The practice of feeding raw meat-based diets to dogs have become popular in recent years. Though there are advantages of this diet since it is a healthier and more natural option, it may harbor bacteria that can become opportunistic and cause infection.
- World Health Organization (WHO). (2020). High levels of antibiotic resistance found worldwide, new data shows. https://www.who.int/
- Finisterra, L., Novais, C., Duarte. B.. Peixe, L., and Freitas, A. (2020). Detection of linezolid-resistant enterococci carrying optrA and/or poxtA in raw-frozen dog foods commercialised in the EU: trend or threat? European Congress of Clinical Microbiology and Infectious Diseases (ECCMID). https://drive.google.com/file/d/1S_3MmNDkU5kPV0ANWp9LIOKpNaZUocGz/view