Scientists have found a strong association between dogs excreting ciprofloxacin-resistant E. coli and feeding them a raw diet.

E. coli, which can lead to food poisoning, is also the United Kingdom’s top cause of urinary tract and bloodstream infections.

Ciprofloxacin belongs to a group of antibiotics called fluoroquinolones, which treat bacterial infections in humans and animals. When E. coli is resistant to antibiotics, infections are more difficult to treat, making patients more likely to be hospitalized and die.

The study examined ciprofloxacin-resistant E. coli in 600 healthy pet dogs in 2019 and 2020. Researchers at the University of Bristol asked owners to complete a survey with details about their dog, the animal’s diet, environments the dog walked in and if their pet had been treated with antibiotics.

When dogs excrete resistant bacteria into the environment and home, there is the potential for these bacteria to be passed on to their owners and other people.

Microbiological and survey data showed that feeding uncooked meat to dogs was the only significant risk factor of those assessed, associated with excretion of the resistant bacteria in the dog’s feces, according to the study published in the journal One Health.  

Human infection risk
Matthew Avison, professor of molecular bacteriology who led the study, said: “Raw meat — whether intended for human consumption after cooking or sold as raw dog food — is likely to be contaminated with antibiotic-resistant E. coli. Cooking kills the bacteria, and good hand hygiene reduces the immediate risk of these bacteria being swallowed and getting into a person’s intestines.

“Choosing to feed a dog raw meat means a person almost certainly has to handle the raw meat, and our research is clear that raw feeding also means pet owners are likely to be interacting with a pet excreting resistant E. coli.”

Avison added that incentives should be given to dog food firms to source meat from farms with good antibiotic usage policies and to test meat for resistant bacteria before selling. Stricter limits should also be set on the amount of bacteria allowed in meat sold to be eaten uncooked, compared to meat cooked before eating.

Samples were collected from 303 rural dogs in 274 households and 297 urban dogs from 289 households. Fluoroquinolone-resistant E. coli were detected in fecal samples from 22 rural and 35 urban dogs.

The study provided evidence for sharing resistant E. coli between dogs, humans, and cattle. Fluoroquinolone-resistant E. coli from rural dogs tended to be of sequence types commonly excreted by cattle. Those from urban dogs mainly carried resistance genes common in human E. coli. 

Researchers previously looked at fluoroquinolone-resistant E. coli from human urinary isolates and dairy cattle fecal samples in the south-west of England.

In 2022, two studies by the University of Bristol found dogs fed on a raw meat diet were more likely to excrete antibiotic-resistant E. coli in their feces.

Dr. Jordan Sealey, a research associate in the School of Cellular and Molecular Medicine (CMM), said: “Individual measures to reduce the risk of resistant bacteria being excreted by dogs include changing to a non-raw food diet or sourcing good quality raw meat that can be cooked, and then cooking it.

“Choosing to feed a dog meat from animals raised on farms in the UK, or other countries with very low usage of critically important antibiotics in farming, may also decrease the risk of them eating resistant bacteria with their dinner.”