Oral Bacteria Confirmed to Selectively Inhibit Periodontal Disease-Associated Bacteria via Nitrite Metabolism - Discovering 'Neisseria' Bacteria as Potential 'Good Oral Bacteria' for Preventing Periodontal Disease

Lion Corporation (President and CEO: Masayuki Takemori) is conducting research based on the belief that, in addition to conventional 'plaque control,' controlling the 'oral bacterial flora' (oral microbiome) to 'balance the bacteria' is crucial for preventing oral diseases. Recently, it was discovered that oral bacteria such as 'Neisseria' selectively inhibit the growth of periodontal disease-associated bacteria by metabolizing nitrite. This research finding is a significant insight that will contribute to a new concept of care for preventing periodontal disease by 'balancing the oral bacteria,' and was presented at the 69th Spring Meeting of the Japanese Society of Periodontology held in Hamamatsu, Shizuoka, from May 22-23, 2026.

Summary of Presentation ① Among oral bacteria, 'Neisseria' species showed high nitrite-metabolizing ability (nitrite reductase activity). ② In an environment where 'Neisseria' and nitrite coexisted, the growth of periodontal disease-associated bacteria was selectively inhibited. These findings suggest that oral bacteria like 'Neisseria' suppress the growth of periodontal disease-associated bacteria by metabolizing nitrite, thereby 'balancing the oral bacteria.' This indicates that 'Neisseria' may be 'good oral bacteria' useful for preventing periodontal disease.

Research Background To prevent cavities and periodontal disease, it is considered important not only to remove plaque through brushing ('plaque control') but also to create a disease-resistant oral environment by 'balancing the oral bacteria.' Hundreds of bacterial species inhabit the oral cavity, and an imbalance increases the risk of conditions like periodontal disease. Recently, attention has focused on 'bacteria abundant in people with good oral health.' Some of these bacteria are known to metabolize nitrite, and it has been reported that the metabolites produced in this process may suppress the growth of certain bacteria. Therefore, our company selected nitrite-metabolizing bacteria from the oral cavity and verified whether their activity actually suppresses the growth of periodontal disease-associated bacteria.

Main Research Results 1. 'Neisseria' bacteria showed particularly high nitrite-metabolizing ability (nitrite reductase activity) We selected 12 candidate bacterial species from the oral cavity that possess genes related to nitrite metabolism and compared their nitrite metabolism rates. The results showed that 'Neisseria' metabolized a particularly large amount of nitrite, demonstrating high nitrite reductase activity.

2. In an environment where 'Neisseria' and nitrite coexisted, the growth of periodontal disease-associated bacteria was selectively inhibited We co-cultured 'N. subflava' (Neisseria), which showed high nitrite metabolism, with the periodontopathic bacterium 'P. gingivalis' and examined changes in the amount of the pathogenic bacteria under different conditions. The results confirmed that the growth of the periodontopathic bacteria was suppressed in the presence of Neisseria and nitrite. Furthermore, we conducted experiments under conditions where multiple bacterial species, including other periodontal disease-associated bacteria like 'F. nucleatum,' formed a biofilm (a bacterial aggregate). The results showed that in the presence of Neisseria and nitrite, the amounts of 'P. gingivalis' and 'F. nucleatum' decreased. In contrast, the amount of another bacterium, 'V. parvula,' did not decrease. When examining the bacterial balance within the biofilm, we confirmed a significant decrease in the proportion of 'P. gingivalis' and 'F. nucleatum.' This result suggests that Neisseria selectively inhibits periodontal disease-associated bacteria by metabolizing nitrite.

These results suggest that oral bacteria such as 'Neisseria' suppress the growth of periodontal disease-associated bacteria by metabolizing nitrite, thereby 'balancing the oral bacteria.' This has shown the potential of 'Neisseria' to be 'good oral bacteria' useful for preventing periodontal disease.

Future Outlook Lion believes that to prevent the recurrence of oral troubles, it is important not only to temporarily eliminate the causative bacteria but also to control the overall balance of bacteria in the oral cavity ('bacterial balance control'). We will continue to contribute to the promotion of overall health starting from the mouth, based on the importance of new preventive methods focusing on 'oral bacterial balance.'

[69th Spring Meeting of the Japanese Society of Periodontology] 〇 Period: May 22-23, 2026 〇 Venue: Act City Hamamatsu 〇 Presentation Date: May 22, 2026 〇 Title: Inhibition of periodontopathic bacteria by nitrite reduction of oral bacteria Presenters: Kanta Obara, Takuma Okuda, Nanaka Ueshima, Kota Tsutsumi, Takashi Chikazawa, Toshikazu Maki (Lion Corporation), Mikari Asakawa, Shinya Kageyama, Toru Takeshita (Kyushu University Graduate School)

Comment from Professor Toru Takeshita, Department of Oral Preventive Medicine, Faculty of Dental Science, Kyushu University Graduate School: 'In our previous epidemiological studies, we reported that Neisseria, one of the resident bacteria everyone has, tends to be dominant in the oral flora of healthy individuals. This study, which shows that Neisseria selectively suppresses the growth of periodontal disease-associated bacteria via nitrite reduction, is a significant achievement suggesting this bacterium's involvement in promoting oral health. While reducing bacteria with brushing and antiseptics is extremely effective for protecting oral health, bacteria are never completely eliminated from the mouth. After a while, disease-related bacteria will grow back. On the other hand, by skillfully utilizing resident bacteria like Neisseria, we might be able to maintain a good oral environment even between brushings. We hope that this approach, focusing on the power of resident bacteria in the oral flora, will become one of the new methods for oral health management.'