Dogs and cats can carry strains of Klebsiella pneumoniae, a bacterium that can cause serious infections in both animals and humans, according to a new study published in the journal Transboundary and Emerging Diseases. While Klebsiella pneumoniae can live in the body without causing harm, it can also lead to infections in the urinary tract, bloodstream, and lungs. The situation becomes more complex when the bacteria become resistant to antibiotics, making infections harder to treat. The research, conducted by scientists from Bournemouth University and University Hospitals Dorset, analyzed 712 samples of Klebsiella pneumoniae collected from dogs and cats across 25 countries. These were compared with more than 38,000 bacterial genomes from humans. This is the first study to provide a global view of the genetic makeup of Klebsiella pneumoniae in pets and compare it on a large scale with human strains. Previous studies had focused on smaller groups, such as individual households or single countries, but this research provides a broader picture of how the bacteria are shared globally between pets and people. The study found that about 87% of the bacteria from pets matched strains previously found in humans. However, the researchers emphasized that this shared genetic background does not prove the bacteria are spreading between pets and their owners. The study also revealed high levels of antibiotic resistance. This occurs when bacteria evolve to survive treatments meant to kill them, which is a major global health issue. In this study, nearly half of the pet-derived samples contained genes that make them resistant to important antibiotics. Cats showed higher resistance rates, with 80% of their samples resistant to multiple drugs, compared to 56% of those from dogs. A particular strain, known as ST147, raised concern. Researchers found that this strain and closely related variants were present in samples from cats, dogs, and humans. Some of these bacteria were nearly identical genetically. Dr. Stephen Fordham, who led the study, said the findings show that similar bacterial strains can be found in both animals and humans, but the study does not suggest that pets are causing illness in people. He emphasized that while pet owners need not be alarmed, the research highlights the importance of including pets in broader efforts to understand and combat antimicrobial resistance.