Raw Pet Food May Contain Antibiotic-resistant Microbes That May be Harmful to Humans

Scientists found high-levels of harmful microbes in raw dog food. Such microbes are resistant even to the most potent antibiotics. Due to the popularity of these raw food diets, pet owners, and humans, in general, are at high risk.

The research shows that some raw-type pet foods contain bacteria that are highly-resistant even to the last-line antibiotics.

Researchers from the Faculty of Pharmacy of the University of Porto in Portugal have analyzed bacteria that are found in both dry and wet processed pet food as well as raw, non-processed pet food from significant brands marketed in Portugal.

The samples in the study included 46 samples from 24 international brands. Twenty-two of these were wet pet food, 15 were dry food, and 9 were raw-frozen pet food. Raw-frozen samples were mostly made of a mixture of different types of meat, fruits, and vegetables.

After culturing bacterial samples, these were tested against several antibiotics. The harmful bacteria called Enterococci and some Enterococcus species, which includes E. faecium, E. faecalis were found in 41 percent of the samples or 19 out of the 46.

The bacteria were found in 8 out of 15 (53 percent) dry pet food, 2 out of 22 (9 percent) wet food samples, and 9 out of 9 (100 percent) in the raw-frozen samples.

All of the raw-frozen samples contained enterococci that were resistant to multiple drugs, including a wide range of antibiotics. One out of the 22 wet food samples contained multidrug-resistant bacteria, while there was none in the dry pet food samples.

Among the nine raw-frozen samples, resistance to the following antibiotics was observed: ampicillin, erythromycin, ciprofloxacin, streptomycin, tetracycline, and chloramphenicol.

Researchers conclude that their study sufficiently demonstrates that raw-frozen-foods marketed for pet consumption carry multidrug-resistant enterococci. It is resistant to last-line antibiotics such as linezolid.

One of the authors of the study, Dr. Ana Freitas, suggests that these raw-frozen foods should at least be cooked after thawing to ensure that drug-resistant bacteria and other harmful microbes are killed. Also, EU authorities who regulate the microbiological safety of these pet foods and conduct a risk assessment of biological hazards should include the determination of antibiotic-resistant bacteria or genes present in these foods, and not just establish the presence of bacterial pathogens such as salmonella.

Scientists have warned that these raw-food based diets for pets might pose an international public health risk if transmission of certain strains occurs between pets and pet owners. The close contact of pets with humans may lead to such transfer as strong evidence show that dogs and humans share common strains of E. faecium that are resistant to multiple drugs.

In research at University Hospital Berlin, Carolin Hackmann and her colleagues identified that 23 out of 45 dogs and 1 out of 71 cats studied had antibiotic-resistant bacteria. The microbes found in two dogs matched the strains of bacteria found in their owners' stool samples. Although the small number indicates pets are not a significant source of resistant bacteria in their owners, it is still smart to protect yourself and your family from antibiotic-resistant illnesses.