Ross Kelly

Scientists have found drug-resistant superbugs harmful to humans in two raw dog-food brands, stirring fresh discussion on the safety of the increasingly popular diets.

The research, conducted in Portugal and presented this month at the European Congress of Clinical Microbiology & Infectious Diseases, raises pressure on governments to more tightly regulate the production of raw pet food.

At least one of the researchers suggests that veterinarians, too, consider warning clients about superbug risks if they haven’t been doing so already.

Antimicrobial resistance, or AMR, occurs when pathogenic microbes evolve to evade drugs meant to kill them, a process that can be hastened by overuse of the drugs. Many scientists consider AMR to be one of the biggest threats to humankind, alongside climate change and nuclear war.

To combat drug resistance, regulators worldwide have been for years discouraging doctors from overprescribing antibiotics and other antimicrobial medications. More recently, the agricultural sector has been urged and compelled to limit the use of antimicrobials in animals raised for food. Less attention has been paid to tackling direct infection risks posed by pet food.

Raw food is of particular concern because many pathogens die when cooked at sufficiently high temperatures, although cooked food, too, can become contaminated.

Scientists at the University of Porto tested 55 samples of dog food, 14 of them frozen raw, for the bacteria Enterococcus, which can cause urinary tract infections, blood infections and meningitis, among other conditions. The samples were taken from various types of dog food — frozen raw, wet, dry, semi-wet and treats — collected from nine retail stores in northern Portugal. The samples encompassed 25 brands, which the researchers did not name. Twenty-one of the brands are sold in multiple countries, including both raw brands.

The researchers were alarmed by the results. Thirty of the 55 samples contained Enterococci, and 26 carried isolates resistant to at least one antibiotic. Enterococci found in all 14 of the raw-frozen samples were resistant to three or more different families of antimicrobial drugs — in other words, they were multidrug resistant. By comparison, multidrug-resistant isolates were found in three samples of cooked products: two wet foods and one treat.

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