E. coli in Pets: A Bacteria with Zoonotic Potential That Poses a Threat to Public Health

A new study highlights the risks of transmission of pathogenic, antibiotic-resistant Escherichia coli bacteria among dogs, cats, and humans.  

Common Urinary Tract Infections in Humans and Animals

Urinary tract infections are among the most common bacterial diseases in humans. They also affect pets, particularly dogs and cats, to a significant extent. In the majority of cases, the causative pathogen is Escherichia coli. It remains to be seen whether these infections, which are common in domestic carnivores, pose a zoonotic risk—that is, whether they can be transmitted from animals to humans. The study provides some concerning findings: certain strains of E. coli responsible for urinary tract infections in dogs and cats show a strong genetic similarity to those isolated from human patients.  

Strains Shared Between Animals and Humans

The researchers collected and analyzed urine samples from dogs and cats with urinary tract infections. Through genetic typing, they identified several serotypes (STs) characteristic of extraintestinal pathogenic strains, known to cause severe urinary tract infections in humans. The results reveal that the ST12, ST127, and ST141 strains, found in animals, are also frequently implicated in human urinary tract infections. Even more concerning, about one-third of the strains studied share a strong genetic similarity with those isolated from human patients. This similarity suggests that the same bacterial clones may circulate between animals and humans living in the same household.  

The Central Role of Antibiotic Resistance

Beyond genetic similarity, the study highlights another aggravating factor: antimicrobial resistance. Some strains isolated from animals produce extended-spectrum β-lactamases or cyclic adenosine monophosphate (cAMP)-type enzymes, rendering several families of antibiotics used in veterinary and human medicine ineffective. Well-known lineages such as ST131 and ST648, often implicated in multidrug-resistant infections in humans, have also been found in pets. The irresponsible use of antibiotics in veterinary medicine is cited as a factor contributing to the selection of these resistant bacterial clones, which can then be transmitted to humans.  

Documented evidence of zoonotic transmission

This risk is not merely a theoretical hypothesis. Previous studies have already described cases of transmission. In 2007, dogs carrying the bacteria were the source of an E. coli O157:H7 outbreak that affected several children. More recently, investigations conducted in veterinary hospitals have revealed the circulation of multidrug-resistant strains between animals and veterinary staff. The similarity in virulence genes observed between human and animal isolates is therefore a strong indicator: pets can act as silent reservoirs of resistant pathogenic strains, posing a tangible risk of transmission to their owners.  

Risk Factors: Diet and Contact

The study also highlights that certain practices increase the risks. Raw meat-based diets (BARF) fed to animals are regularly cited as a source of pathogenic strains, particularly shigatoxin-producing E. coli (STEC). These bacteria can infect animals and then be transmitted to humans through close contact. Physical proximity between owners and pets—such as sharing a bed, licking, or handling litter—increases the opportunities for bacteria to pass from one host to another.  

Implications for Public Health and Animal Health

These findings raise major public health concerns. Urinary tract infections are already difficult to treat when the strains are multidrug-resistant. If pets become vectors for these strains, treatment strategies could become even more complex. The researchers advocate for enhanced surveillance based on a “One Health” approach that integrates human health, animal health, and environmental health. Their recommendations include:

• a use reduction in antibiotics in veterinary medicine;
• systematic epidemiological surveillance of urinary tract infections in animals;
• educating pet owners on proper hygiene and feeding practices;
• close monitoring of bacterial strains circulating between animals and humans.