An analysis of pet food made from raw meat by researchers from the University of Zurich has found Salmonella and E. coli.

Numerous recalls of raw pet food because of those pathogens have been posted in the United States in the past couple of years. Some human infections were confirmed.

The study out of Zurich evaluated commercially available raw meat-based diets (RMBDs) with regard to microbiological quality and antimicrobial resistant (AMR) Enterobacteriaceae. Findings were published in the Royal Society Open Science journal.

Meat-eating pets, mainly dogs, are increasingly being fed raw meat, animal by‑products, bones and additional food such as fruit and vegetables. Proponents call this mix BARF (Biologically Appropriate Raw Food).

However, researchers believe BARF diets are a significant risk factor for the spread of antibiotic-resistant bacteria when pet owners come into contact with the bacteria when preparing food. Another reason is pets have close contact with humans, increasing risk of transmitting the bacteria.

Almost three quarters failed EU micro standards
Researchers tested 51 raw dog food samples from various suppliers in Switzerland to find the total number of germs present, for normal and antibiotic-resistant enterobacteria and Salmonella. They were collected in September and October 2018 and contained meat from Switzerland and Germany.

AMR bacteria were found in 32, or 62.7 percent, of samples and most were resistant to third-generation cephalosporins due to production of extended-spectrum β-lactamases (ESBLs). Resistant bacteria in raw food can be transmitted to the pets and also to humans.

A total of 72.5 percent of food samples did not meet the microbiological standards on Enterobacteriaceae set out by EU regulations for animal by-products intended for pet food. Salmonella was found twice, as were E. coli harboring the colistin-resistance gene mcr-1.

“The situation with the multidrug-resistant bacteria has spiraled out of control in recent years. Urgent measures are needed to tackle the spread of ESBL-producing germs,” said Roger Stephan, professor at the Institute for Food Safety and Hygiene of the Vetsuisse Faculty at the University of Zurich.

Isolated Salmonella and E. coli
Salmonella species were isolated from two RMBDs. Serotypes were monophasic Salmonella Typhimurium 4,12:i:- isolated from pet food containing lamb and Salmonella London from turkey.

E. coli harboring the colistin-resistance gene mcr-1 were identified in two samples. One contained offal of horse, and the other was minced quail meat. ESBL-producing Enterobacteriaceae were isolated from 31 RMBDs. Analysis of 42 E. coli isolates identified 28 different sequence types.

Resistance profiles were determined for 50 isolates. Resistance to cefotaxime and cefepime was seen for 44 and five of the isolates. None of them were resistant to nitrofurantoin.

Magdalena Nüesch-Inderbinen, first author in the study, said finding ESBL-producing bacteria in over 60 percent of the samples was worrying.

“They included several types of E. coli which can cause infections in humans and animals. We therefore advise all dog and cat owners who want to feed their pets a BARF diet to handle the food carefully and maintain strict hygiene standards. Pet owners should be aware of the risk that their pet may be carrying multidrug-resistant bacteria and can spread them.”

Another study, published earlier this year in the journal Veterinary Record, detected enterobacteriaceae in all 60 frozen samples of RMBD. Salmonella species were found in four and Campylobacter in three samples.

A different study, published in the same journal, found foodborne pathogens are rarely transmitted to humans through raw pet food but reports of outbreaks linked to pet treats and dry food can be found.

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