Dogs and cats may carry strains of Klebsiella pneumoniae — a potentially serious bacterium that can cause infections that are also found in humans, according to new research from Bournemouth University.
Klebsiella pneumoniae can live harmlessly in the body but can also cause serious infections, including infections of the urinary tract, bloodstream and lungs. The problem becomes more difficult to treat when the bacteria are resistant to antibiotics.
The research team from Bournemouth University and University Hospitals Dorset analysed 712 samples of the bacteria collected from dogs and cats across 25 countries and compared them with more than 38,000 genomes from people.
The study is the first to map the global genetic makeup of Klebsiella pneumoniae carried by domestic dogs and cats, and to compare it on a large scale with the same bacteria in people. Earlier research had looked at individual households, veterinary clinics or single countries, but the wider global picture in pets had not been established until now.
Around 87% of the bacteria from the animals belonged to strains that have also been identified in people. The researchers stress that this shared genetic background does not, on its own, show that the bacteria pass between pets and their owners.
The study, published in the journal Transboundary and Emerging Diseases , also found a high level of antibiotic resistance.
Antibiotic resistance occurs when bacteria develop the ability to survive medicines designed to kill them or stop them from spreading. It is a global concern because bacteria can be resistant to several types of antibiotics, leaving doctors and veterinarians with fewer treatment options.
Nearly half of the animal-derived samples in this new study carried genes known to be resistant to clinically important antibiotics. Resistance was particularly widespread among bacteria collected from cats: 80% of samples from cats were classified as resistant to multiple drugs, compared with 56% of those from dogs.
One strain in particular, known as ST147, raised concern. Researchers identified a closely related group of this strain in samples from cats, dogs and people. Some of these bacteria were almost genetically identical.
Dr Stephen Fordham, Lecturer in Biosciences at Bournemouth University who led the study said, “This study does not tell us that our pets are making us ill, but it does show is that very closely related bacterial strains can be found across animals and humans. There is no need for owners to be concerned but this does show the importance of including our pets in wider efforts to understand and tackle antimicrobial resistance.”
Transboundary and Emerging Diseases
Imaging analysis
Animals
Companion Animals Harbour Globally Circulating Human-Associated Klebsiella pneumoniae Lineages and High-Risk Antimicrobial Resistance Clones
28-Aug-2026