The purpose of this study was to determine any potential antibacterial effects of gatifloxacin on Porphyromonas gulae, a canine periodontal infection. Investigated were gatifloxacin's minimum inhibitory concentrations (MIC) and its bactericidal properties. The canine periodontopathic bacteria were evaluated in broth, and gatifloxacin prevented their development. P. gulae was discovered to be effectively inhibited at a MIC of 50 nM. The adenosine triphosphate bioluminescence experiment revealed that gatifloxacin had concentration-dependent bactericidal effects on the tested microorganisms. Rat bone marrow mesenchymal stem (BMMS) cells were treated with gatifloxacin in order to determine whether it was safe to do so. The vitality of the treated BMMS cells was then measured. During a 3-day culture, about 80% of BMMS cells that were given 100 nM gatifloxacin survived. These findings suggest the possibility of using locally given gatifloxacin to prevent canine periodontal infection.