Comparison of microbiome profiles across sample types in patients with peri-implantitis using 16S rRNA sequencing

Abstract

Purpose: Numerous studies have applied microbial analyses to peri-implantitis, including analyses of samples collected from various sites. While characteristics of the peri-implantitis microbiome have been identified, differences in sampling methods between studies have not been considered. The present study aimed to (1) characterize microbial similarities among saliva, gingival crevicular fluid (GCF), subgingival plaque (SGP) and inflammatory connective tissue (ICT) within the same participant with peri-implantitis; and (2) determine the microbial profiles of peri-implantitis sites. Methods: Saliva, GCF, and SGP samples were collected from 18 patients undergoing periimplantitis surgery, and ICT samples were obtained after flap elevation. The collected samples were analyzed using 16S rRNA sequencing. Results: The sampling sites showed a mean bone loss of 6.9 mm and a maximum probing depth (PD) of 8.3 mm. Alpha diversity did not differ significantly among ICT, GCF, and SGP, whereas saliva exhibited a distinct diversity profile. Additionally, beta diversity analyses indicated that the microbial community structure differed significantly between saliva and the other samples. In taxonomic analyses, the microbial profiles of ICT, GCF, and SGP were clearly distinguishable from those of saliva. Saliva had lower proportions of Bacteroidetes and higher proportions of Proteobacteria and Actinobacteria species, especially at sites with deep PD. Pearson correlation analyses revealed strong correlations between ICT and both GCF and SGP, but not between ICT and saliva. Pathogenic species such as Porphyromonas gingivalis, Tannerellaforsythia, Treponema denticola, Campylobacterrectus, Filifactoralocis, and Porphyromonas endodontaliswere more abundant in ICT than in saliva. Conclusions: ICT, GCF, and SGP shared similar microbial profiles, whereas saliva exhibited a significantly different profile. ICT, GCF, and SGP had higher abundances of peri-implant pathogenic species, whereas saliva tended to have lower abundances; this difference was especially pronounced in deep pockets.