Reduced salivary secretion contributes more to changes in the oral microbiome of patients with primary Sjögren's syndrome than underlying disease

The oral microbiome of patients with primary Sjogren’s syndrome (pSS) differs from that of healthy individuals.1–3 Whether these changes are the consequence of reduced salivary secretion or specific for pSS is yet unknown. Therefore, the aim of our study was to assess whether patients with pSS have a specific oral microbiome compared with symptom controls (patients without SS, indicated as non-SS patients) and healthy controls (HCs). To capture the overall bacterial composition in the mouth, we collected oral washings instead of buccal swabs from 121 consecutive patients referred for a diagnostic pSS workup and 14 volunteers without oral or ocular dryness (HCs). Patients fulfilling the 2016 American College of Rheumatology/European League Against Rheumatism classification criteria were classified as pSS (n=36) and patients not fulfilling the criteria as non-SS (n=85) (table 1).4 View this table: Table 1 Patient characteristics* Bacterial composition was assessed with 16S rRNA gene sequencing of the V4 region. Reads were processed and diversity was analysed with QIIME V.1.9.1.5 All samples were equated to 8000 reads/sample. Comparative statistics were performed in R V.3.4.2.6 For details see online Supplementary text. ### Supplementary file 1 [SP1.docx] Alpha diversity, that is, the number of bacterial taxa and proportion in which each taxon is represented per sample was measured by the number of observed operational taxonomic units and Shannon index. Alpha diversity was similar between pSS, non-SS and HCs, indicating that oral washings of …