16S rRNA gene amplicon sequencing of whole saliva, supragingival plaque, buccal and dorsal tongue mucosa in primary Sjogren's syndrome and non-Sjogren's syndrome sicca patients

Objective: This study aims to determine if the microbiota in four different oral sites and the oral health status differs between patients with primary Sjogren's syndrome (pSS), non-pSS sicca symptoms, and healthy controls.Methods: Stimulated whole saliva (SWS), supragingival plaque (SGP), buccal mucosa tissue (BLM) and tongue scrape (TGS) samples from 23 pSS patients, 36 patients with sicca symptoms, not fulfilling the classification criteria for pSS (non-pSS sicca), and 21 age-matched healthy controls (HC) were analyzed using V3-V4 16S rRNA gene amplicon sequencing, and determination of amplicon sequence variants (ASVs).Results: PSS and non-pSS sicca patients did not differ with respect to oral health status, saliva flow rates, abundance of predominant genera, relative abundance on genus level or bacterial diversity in any of the sites. Both patient groups differed significantly from the healthy control group in the abundance of 61 ASVs across all sites. The alpha-diversity was lower in SGP from non-pSS sicca patients (p = 0.019), and in TGS from pSS patients (p = 0.04). The proportion of variation in the beta-diversity across all four sites could be explained by the diagnosis (pSS, non-pSS sicca, and HC). Subgrouping of patients according to their salivary flow rates (SWS >0.7 ml/min versus SWS <=0.7 ml/min), revealed significantly different abundance of three ASVs in SWS, 11 in SGP, and six in TGS.Conclusion: Our findings suggest that changes in the microbiome at different oral sites are caused by severe salivary gland hypofunction, and not pSS itself.