Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 5 2025 10 14 718 724 Shahram Jamshidi Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Matin Mozafari Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Masoomeh Khanipour Machiani Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Mahdi Bashizade Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran 2025 03 05 2025 09 01 Background and Objectives: Helicobacter and Wolinella are gram-negative bacteria belonging to the Helicobacteraceae family. While Helicobacter species are well-known for their role in gastric disorders, emerging evidence suggests their presence in the oral cavity and potential involvement in periodontal diseases. Materials and Methods: Helicobacter and Wolinella species were investigated in 122 saliva and periodontal plaque samples from dogs and cats by DNA extraction, PCR amplification, and 16S rDNA gene identification. Results: Comparing the periodontitis group and the healthy group, a higher incidence of positive Wolinella and Helicobacter species was shown in both dog and cat groups. 16S rDNA genes of Helicobacter were detected in 60% of the cats and 67.7% of the dogs. Detection of 16S rDNA genes of the Wolinella group in felines was 78.3% which was higher than in canines (67.7%). Helicobacter felis (35%) was the most common species detected in cats, contrary to dogs, in which Helicobacter heilmannii (30%) detection was higher (in both groups). Helicobacter pylori was not detected in either group. Conclusion: Comparing the occurrence of Helicobacter and Wolinella in the mouths of dogs and cats, their association with periodontal disease, and the possibility of a common source of infections between humans and companion animals is of great importance for the management of oral health in animals and humans. https://ijm.tums.ac.ir/index.php/ijm/article/view/5330 https://ijm.tums.ac.ir/index.php/ijm/article/download/5330/1817