In the journal “Royal Society Open Science,” University of Zurich scientists wrote that the prevalence of antimicrobial-resistant bacteria and Salmonella in raw meat pet food poses a "severe health risk," especially to infants, the elderly, pregnant or immunocompromised individuals.

Researchers found strains of antimicrobial-resistant bacteria in 62.7% of raw meat dog and cat foods they tested. The scientists analyzed 51 varieties of raw pet food that the team purchased in Switzerland. Levels of Enterobacteriaceae, the bacterial family of E. coli and Salmonella, exceeded European Union regulations in 72.5% of the raw dog and cat foods. They detected Salmonella itself in 3.9% of the samples.

The Swiss researchers found that many of the antimicrobial-resistant bacteria produced certain enzymes, called extended-spectrum β-lactamases (ESBLs). This enzyme grants the bacteria resistance to medically important antibiotics, called third-generation cephalosporins.

E. coli harboring a gene for colistin resistance contaminated two raw pet food samples. Colistin serves as a last-resort bulwark against multidrug resistant bacteria.

Raw meat pet food tested

In September and October 2018, researchers purchased 47 raw-meat based pet foods from six cities within 300 kilometers of their laboratory. Another four samples came from a small-scale raw meat pet food producer in Switzerland. That small producer was certified based on hazard analysis and critical control points (HACCP) hygiene standards.

All of the raw meat pet foods used in the study contained only uncooked meat or organs without any preservation, such as pasteurization or drying. After purchase, the products were transported in bags containing coolants and stored at below freezing. The meats in the products included beef cattle, poultry, horse, lamb, moose, ostrich, rabbit and fish. The ingredients came from Switzerland or Germany.