Microbe-Microbe Interaction As A Virulance Factor In Periodontitis

Introduction: Periodontitis is a chronic poly-microbial disease, in which several bacteria are associated with its etiology. Porphyromonas gingivalis and Fusobacterium nucleatum are considered important pathogens in periodontitis`s pathogenesis. Coaggregation between these bacteria occurs by specific binding of F.nucleatum`s outer membrane protein to P.gingivalis`s polysaccharide, and is partially mediated by P.gingivalis`s capsule. In previous studies we have shown that P.gingivalis and F.nucleatum mixed-infection results in robust inflammation and augmented bone loss. Objectives: To characterize the role of coaggregation between P.gingivalis and F.nucleatum in an experimental periodontitis model, and lucid the role of P.gingivalis capsule in this phenomenon. Methods: Mice were orally infected with mixed-infection P.gingivalis and F.nucleatum with and without coaggregation and with the use of capsulated or non-capsulated strains of P.gingivalis. The inhibition of coaggregation was achieved by lactose. Six weeks following the infection, the maxillary jaws were harvested and analyzed for alveolar bone loss using microCT. Results: Capsulated P.gingivals coaggregates stronger with F.nucleatum compared with uncapsulated P.gingivalis. The addition of lactose eliminated coaggregation either with capsulated or non-capsulated P.gingivalis. Mice orally infected with F.nucleatum and P.gingivalis induced significant bone loss compared with the non-infected group. The mixed-infection using capsulated P.gingivalis resulted in augmentation of bone loss compared with mixed-infection using non-capsulated P.gingivalis. The addition of lactose to the mixed infection with capsulated P.gingivalis resulted in reduction of bone loss compared with the same group without lactose. However, the addition of lactose to mixed infection using non-capsulated P. gingivalis, resulted in increased bone loss compared with the same group without lactose. Conclusion: Coaggregation between F.nucleatum and capsulated P.gingivalis is stronger than with non-capsulated P.gingivalis. The elimination of coaggregation in mixed infection with capsulated P.gingivalis reduces the virulence of the infection, while in the mixed infection with non-capsulated P.gingivalis it augmented the bone loss.