Adhesion and Invasion of Fusobacteria to Epithelial Cells

Fusobacteria are involved in several infectious processes of the oral cavity. Objectives: Various fusobacteria strains were studied for their adhesion and invasion capacity to epithelial cells. Methods: Subconfluent cultures of HaCat human skin keratinocytes were infected with clinical and ATCC strains of F. nucleatum, F. necrophorum and F. mortiferum. Adhesion and invasion of the bacteria were assayed by culturing the epithelial cell-associated bacteria before and after antibiotic treatment that kills the adhered but not the intracellular bacteria. Proliferation of the epithelial cells was studied with the CellTiter 96 kit. Results: All the tested fusobacteria species adhered and invaded the epithelial cells, although there were considerable differences in the strains. The bacteria were able to multiply intracellularly but by 12 h of culture most of the bacteria were dead. Intracellular replication required reorganization of epithelial actin filaments because the treatment of the infected epithelial cells with cytochalasin D markedly reduced the number of living intracellular bacteria. The tested fusobacteria also increased the number of epithelial cells in culture. Conclusions: Fusobacteria are able to adhere to and invade epithelial cells, and increase their proliferation. Thereby they are able to survive in oral tissues and participate in various disease processes.