Raw Pet Food A Source Of Superbug Fatal To Humans, Study Warns

People who feed their dogs raw pet food may find more on the menu than they bargained for, with a new study finding it may be a source of antibiotic-resistant bacteria that could ultimately threaten humans, Alan Mozes of HealthDay reported for MedicineNet.

The European analysis looked at 55 wet, frozen, dry, semi-wet and treat-version dog food samples sourced from 25 different brands. Some of the food was raw; some was not. Raw samples included duck, salmon, turkey, chicken, lamb, goose, beef and vegetable varieties.

More than half (54%) of the raw samples contained a bacteria called Enterococci, and 4 in 10 of enterococci-laced samples contained a form of the bacteria that was determined to be multi-drug resistant.

That means the bacteria did not respond to standard antibiotics. Equally alarming, investigators said, is that nearly a quarter (23%) of the enterococci-contaminated samples also didn't respond to the antibiotic linezolid, a last-resort antibiotic that is only used for very severe infections that prove untreatable with any other antibiotic.

And this may not be a problem solely for dogs, said study author Ana Freitas. She's an investigator with UCIBIO (Research Unit on Applied Molecular Biosciences), an organization is hosted by REQUIMTE, a collaboration between the University of Porto and the NOVA University of Lisbon, both in Portugal.

"Antibiotic-resistant bacteria threaten our lives because human infections, from common ones to more severe ones, are harder to treat, if treatable at all," Freitas explained. In fact, an additional genetic analysis revealed that the resistant bacteria identified in raw dog food samples was virtually identical to resistant bacteria found in hospital patients across the United Kingdom, Germany and the Netherlands. That does not, however, mean that raw dog food inevitably puts human life at risk, said Freitas, but it's not good news either.

Freitas and her colleagues will report their findings this week at a virtual meeting of the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID). Such research is considered preliminary until published in a peer-reviewed journal.

Freitas' study was not the only research presented at the meeting on the relationship between dogs, their owners and antibiotic-resistant bacteria. A gene that confers resistance to a last-resort antibiotic can be passed from dogs to their owners, another group of Portuguese researchers reported. The mcr-1 gene -- first reported in China in 2015 -- provides resistance to colistin, an antibiotic of last resort.

There are fears the gene could combine with drug-resistant bacteria to spawn an untreatable type of infection. To find out if household pets may be acting as a reservoir of the gene and helping it spread, the researchers analyzed fecal samples from 126 healthy people living with 102 cats and dogs in 80 households in Lisbon. They found the gene in four people and two pet dogs.

In two cases, both the dog and its owner had the gene. No cats were carrying the gene. "Colistin is used when all other antibiotics have failed -- it is a crucial treatment of last resort. If bacteria resistant to all drugs acquire this resistance gene, they would become untreatable, and that's a scenario we must avoid at all costs," study author Juliana Menezes, from the University of Lisbon's Centre of Interdisciplinary Research in Animal Health, said in an ECCMID news release.

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