Oral and Intestinal Bacterial Flora in Patients with Increased Periodontal Inflamed Surface Area: A Cross-Sectional Study.

Background/Objectives: Periodontitis is caused by bacterial plaque. The oral microflora may interact with the intestinal microflora and play a role in the development of periodontitis. The periodontal inflamed surface area (PISA) has been shown to be a useful indicator of periodontal disease related to systemic diseases; however, few studies have shown an association between PISA and the bacterial flora. This study aimed to determine the association between PISA and oral and intestinal bacteria. Methods: Participants were recruited between 2018 and 2021 at the Medical and Dental Collaboration Center of Kanagawa Dental University Hospital. A periodontal clinical examination was performed, and the PISA was calculated. Salivary tests were conducted, and leukocyte scores in the saliva were calculated. Moreover, 16S rRNA amplicon sequencing was performed using saliva and stool samples to analyze oral and intestinal bacteria, respectively. Results: Higher PISA levels resulted in an increased presence of Bacteroides and a decreased presence of Proteobacteria and Actinobacteria in the saliva. An increase in Bacteroides was detected in the saliva of patients with high leukocyte scores. No correlation was observed between PISA and intestinal bacteria. Conclusions: Bacteroides was highly abundant in the saliva of patients with worsened periodontal conditions, as indicated by PISA. No association was found between PISA and intestinal bacteria.