Correlations among core species corresponding to the clinical staging of periodontitis

The correlation between microbiota plays a vital role in the progression of periodontal disease. This study investigated the in situ interaction networks between periodontal pathogens in periodontal and peri-implant disease. We used quantitative real-time polymerase chain reaction and Pearson’s correlation coefficients to quantify the copy numbers and correlations of four oral core species—Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, and Streptococcus gordonii—from 80 subgingival sites (healthy and with periodontitis or gingivitis) in patients with periodontitis, and 68 subgingival sites (healthy and with periodontitis, gingivitis, peri-implantitis, or peri-implant mucositis) in patients with implants. The highest bacterial counts were observed for Porphyromonas gingivalis and Prevotella intermedia at all the sites. Within the same cohorts, the bacterial loads were greater at diseased sites than at healthy sites. Bacterial counts did not differ among clinical sites in the same group (P > 0.05) but differed between periodontitis and peri-implant mucositis sites in the two groups. Porphyromonas gingivalis, F. nucleatum, and Prevotella intermedia had strong correlations at gingivitis and healthy sites and moderate correlations at periodontitis sites in patients with periodontitis. In patients with implants, Prevotella intermedia, F. nucleatum, and S. gordonii had strong correlations only at peri-implantitis sites. Also, based on metagenomic analysis, F. nucleatum and Prevotella intermedia were significantly correlated at the subgingival plaque in peri-implantitis and periodontitis samples. Our results suggest that variations in microbe-microbe interactions in subgingival plaque reflect changes in the progression of periodontal disease, providing a new perspective for understanding the mechanisms of periodontitis and peri-implantitis.