Analysis of Salivary Microbiome and Its Association With Periodontitis in Patients With Obstructive Sleep Apnea

Abstract

Objectives: This study aimed to analyze the periodontal conditions of patients with obstructive sleep apnea (OSA) in relation to the salivary microbiome.

Materials and methods: In total, 54 male adults (27 with OSA, 27 controls) completed this cross-sectional study. All participants were monitored by overnight polysomnography (PSG) and underwent full-mouth periodontal examination. Saliva samples were then collected, and the microbial 16S ribosomal RNA gene was sequenced. The data were analyzed to determine the microbial distribution and the community structure of the two groups.

Results: Demonstrated by alpha and beta diversity, the OSA group had a lower microbial richness and a lower observed species than the controls. There was no significant difference in the microbial species diversity or evenness between the OSA and the non-OSA groups. The OSA group had fewer operational taxonomic units (OTUs), and the distribution of microbiome showed that several gram-positive bacteria had higher abundance in the OSA group. As for periodontal pathogens, the relative abundance of Prevotella was significantly increased in the OSA group. No significant difference was observed in the relative abundance of other pathogens at either the genus or species level.

Conclusions: The salivary microbial community structure was altered in patients with OSA in terms of species richness and trans-habitat diversity, along with an increase in Prevotella, a specific periodontal pathogen. These findings might explain the high prevalence of periodontitis in OSA patients.

Keywords: 16S rRNA gene sequencing; obstructive sleep apnea; periodontal pathogens; periodontitis; salivary microbiome.

Figure 1

Species accumulation and rarefaction analysis indicated that the sample size is sufficient enough to represent the species composition. (A) Sample-based species accumulation curve and (B) Sample-based rarefaction curve gradually became flat with the increasing number of sequencing samples.

Figure 2

Alpha diversity analysis of the salivary microbial samples. (A) Chao1 Index; (B) Observed species; (C) Shannon Index; (D) Simpson Index; (E) Goods coverage; (F) Pielou’s evenness. The Chao1 and observed species were significantly decreased in the OSA group. Goods coverage were significantly higher in the OSA group. There was no significant difference of Shannon, Simpson and Pielou’s evenness between the two groups. *p < 0.05 was considered statistically significant.

Figure 3

Beta diversity analysis of the salivary microbial samples. (A) Principal Coordinates Analysis (PCoA) calculated by the relative abundance of OTUs. Salivary microbial samples were divided into four categories. OSA-P, OSA/periodontitis; OSA-nP, OSA/non-periodontitis; nOSA-P, non-OSA/periodontitis; nOSA-nP, non-OSA/non-periodontitis. The communities of the four categories had the tendency to cluster apart from each other. (B) The average weighted UniFrac distance value of the OSA group is slightly higher than the non-OSA group.

Figure 4

Analysis of the composition and structure of microbial communities at the genus level. (A) Venn diagram to visualize the shared and unique OTUs in the OSA and the non-OSA group. (B) Heatmap of the relative abundance of salivary microbiome at the genus level of each participant. (C) The relative abundance and distribution displaying the top-most significantly different taxa at phylum, genus, and OTU levels between the OSA and the non-OSA group.

Figure 5

Analysis of the relative abundance of specific genus and species related to periodontitis. (A) The relative abundance of the periodontal pathogens at the genus level. Only Prevotella was more abundant in the OSA group. (B) The relative abundance of the periodontal pathogens at the species level. No significant difference was observed in the selected five species between two groups.