The present invention relates to novel bacterial isolates identified by their 16S rRNA DNA, that cause periodontal disease in companion animals, polynucleotide sequences contained therein, polypeptides encoded by such polynucleotide sequences and vaccines comprising such bacteria, polynucleotides, or polypeptides. Also provided are methods for treating and preventing periodontal disease and kits for detecting and treating periodontal disease kits for detecting and preventing periodontal disease.