Predominant bacterial species in subgingival plaque in dogs.

BACKGROUND AND OBJECTIVE: The dog has been used extensively for experimental and microbiological studies on periodontitis and peri-implantitis without detailed knowledge about the predominant flora of the subgingival plaque. This study was designed to evaluate the predominant cultivable bacterial species in dogs and compare them phenotypically and genotypically with corresponding human species. MATERIAL AND METHODS: Four subgingival samples were taken from two upper premolars in each of six Labrador retrievers. The samples from each dog were processed for anaerobic culture. From the samples of each dog, the five or six predominating bacteria based on colony morphology were selected and pure cultured. Each of the strains was characterized by Gram stain, anaerobic/aerobic growth and API-ZYM test. Eighteen strains showing clear-cut phenotypic differences were further classified based on DNA sequencing technology. Cross-reactions of DNA probes from human and dog strains were also tested against a panel of both human and dog bacterial species. RESULTS: Thirty-one strains in the dogs were isolated and characterized. They represented 21 different species, of which six belonged to the genus Porphyromonas. No species was found consistently in the predominant flora of all six dogs. Porphyromonas crevioricanis and Fusobacterium canifelinum were the two most prevalent species in predominant flora in dogs. DNA probes from human and dog species cross-reacted to some extent with related strains from humans and dogs; however, distinct exceptions were found. CONCLUSION: The predominant cultural subgingival flora in dogs shows great similarities with the subgingival bacteria from humans at the genus level, but distinct differences at the species level; however, a genetic relatedness could be disclosed for most strains investigated.