Impact of periodontal therapy on the subgingival microbiota of severe periodontitis: comparison between good responders and individuals with refractory periodontitis using the human oral microbe identification microarray

Abstract

Background: This study compares the changes to the subgingival microbiota of individuals with "refractory" periodontitis (RP) or treatable periodontitis (good responders [GR]) before and after periodontal therapy by using the Human Oral Microbe Identification Microarray (HOMIM) analysis.

Methods: Individuals with chronic periodontitis were classified as RP (n = 17) based on mean attachment loss (AL) and/or >3 sites with AL ≥2.5 mm after scaling and root planing, surgery, and systemically administered amoxicillin and metronidazole or as GR (n = 30) based on mean attachment gain and no sites with AL ≥2.5 mm after treatment. Subgingival plaque samples were taken at baseline and 15 months after treatment and analyzed for the presence of 300 species by HOMIM analysis. Significant differences in taxa before and post-therapy were sought using the Wilcoxon test.

Results: The majority of species evaluated decreased in prevalence in both groups after treatment; however, only a small subset of organisms was significantly affected. Species that increased or persisted in high frequency in RP but were significantly reduced in GR included Bacteroidetes sp., Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella spp., Tannerella forsythia, Dialister spp., Selenomonas spp., Catonella morbi, Eubacterium spp., Filifactor alocis, Parvimonas micra, Peptostreptococcus sp. OT113, Fusobacterium sp. OT203, Pseudoramibacter alactolyticus, Streptococcus intermedius or Streptococcus constellatus, and Shuttlesworthia satelles. In contrast, Capnocytophaga sputigena, Cardiobacterium hominis, Gemella haemolysans, Haemophilus parainfluenzae, Kingella oralis, Lautropia mirabilis, Neisseria elongata, Rothia dentocariosa, Streptococcus australis, and Veillonella spp. were more associated with therapeutic success.

Conclusion: Persistence of putative and novel periodontal pathogens, as well as low prevalence of beneficial species was associated with chronic refractory periodontitis.

Figure 1

Bar chart of the frequency of bacterial species/cluster in subgingival samples from all subjects at baseline and 15 months post-therapy, and from sites that lost ≥2.5 mm of attachment (“refractory” sites) post-therapy in “refractory” periodontitis patients. OT means oral taxon designation. ^*Refers to significant differences between all samples at baseline and post-therapy. ^†Refers to significant differences between samples from “refractory” sites and sites at 15 months post-therapy. ^‡Refers to significant differences between samples from “refractory” sites and sites at baseline (p<0.05, Chi-square test).

Figure 2

Bar chart of changes in mean frequency (±SD) of bacterial species from baseline to post-therapy in samples from “good responders” (GR) and “refractory” periodontitis (RP) subjects. OT means oral taxon designation. *Refers to significant differences between baseline and post-therapy in the GR group. ^†Refers to significant differences between baseline and post-therapy in the RP group (p<0.05; Wilcoxon test).