Active Microbiota Show Specific Correlationships in Peri-implantitis and Periodontitis

Peri-implantitis is an oral inflammatory disease that is representative of polymicrobial diseases, and it leads to dental implant failure and systemic diseases. Although its clinical symptoms are similar to those of periodontitis, its progression is more difficult to suppress. For effective infection control, differences among intraoral pathogens and their ecology must first be elucidated. In this study, we used both 16S rDNA and 16S rRNA sequence data to determine core bacteria with activity in situ. Moreover, we used the 16S rRNA/16S rDNA ratio as a bacterial activity index and predicted bacterial community functions. Furthermore, we analyzed correlation coefficient networks for each high-activity species pair. As a result, the community structure of core bacteria with high activity differed from that of the core microbiome determined by only 16S rDNA. Moreover, there was no correlation between relative abundance based on 16S rDNA or 16S rRNA profile and the bacterial activity index value. Furthermore, despite the conspicuous difference in bacterial composition not only between peri-implantitis and periodontitis but also between research participants with the same disease, the predicted functional profiles of the 2 diseases were quite similar. Finally, we revealed that the bacterial species forming the core connection of the co-occurrence network and its structure were quite different between the 2 diseases. The network analysis implies that the structure of the core connection in peri-implantitis is simpler than that in periodontitis, and contains Capnocytophaga gingivalis as a hub species. These data may provide a possible explanation for the differing tractability of these diseases.