**6. Conclusions**

The oral cavity is suggested as the reservoir of bacterial infection, and the oral and pharyngeal biofilms formed by oral bacterial flora have been found to be associated with various systemic diseases such as cardiovascular disease, arteriosclerosis, and diabetes. With the increasingly aging society, the rate of the elderly people with compromised immune function that are susceptible to infection is high and the onset and spread of infectious diseases among elderly people in nursing homes have become a major social problem. Therefore, the establishment of more e ffective prevention and treatment methods to reduce or minimize bacterial biofilm-related infectious diseases and their systemic complications is desired. However, even now, it has been pointed out that abuse of antibiotics for biofilm infections leads to the acquisition of antibiotic resistance and the emergence of higher toxic pathogens, such as emergence of multidrug resistant bacteria. In order to solve these problems, the development of therapeutic methods to e ffectively suppress the bacterial attachment, colonization, and biofilm formation without selective pressure, not for selective measures based on the conventional antimicrobial sensitivity or the mechanism of antimicrobial action, is expected. Regarding biofilm, which is the cause of bacterial infections, and considering its life cycle and its pathogenic factors, nucleic acids, such as DNAs that are commonly possessed by microorganisms, DNA binding proteins widely structurally conserved among microorganisms, and cyclic-di-GMP, intracellular second messenger involved in bacterial virulence and biofilm formation, may possibly be considered as target molecules to prevent and treat biofilm infections. Nucleic acids and their receptors are attracting attention as targets for the development of therapeutics not only for infectious diseases but also for other systemic diseases, such as autoimmune diseases and cancer. Therefore, the development of further research is expected.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
