Oral infectious diseases, such as dental caries and periodontitis, are caused by oral biofilm, so-called dental plaque. The foundation of the biofilm structure is the extracellular polymeric substances consisting of polysaccharides, toxins, proteins and nucleic acids as well as vesicles, which secrete these components outside of bacterial cells. Among them, extracellular DNA(eDNA) has become increasingly recognized as a key component for biofilm formation and its structural stability. Bacterial histone-like DNA binding protein(HLP), an accessory architectural protein in a variety of bacterial cellular processes due to DNA and mRNA binding capacity, also contributes to the activation of host innate immunity during bacterial infection. Moreover, it has been suggested that vesicles harboring DNA are associated with horizontal gene transfer. In recent two decades, numerous studies regarding the association between oral biofilm infectious diseases and various systemic diseases, such as cardiovascular diseases, atherosclerosis, diabetes mellitus, aspiration pneumonia and autoimmune diseases, have been reported. Besides bacteria, Candida spp., which are frequently implicated in mixed bacterial-fungal infections in humans, can readily form biofilms on the surfaces of denture and cause a variety of infectious diseases ranging from denture stomatitis in denture wearers to life-threatening invasive infections, such as aspiration pneumonia, particularly in immunocompromised and elderly populations. From the viewpoint of biofilm infection, which cause systemic diseases as well as oral infectious diseases, the development of new preventive and therapeutic procedures targeting bacterial-derived pathogenic factors such as eDNA, HLP and vesicle, is expected in future studies.
