Salivary microbiota from primary Sjögren's syndrome patient

Primary Sjögrens's syndrome (pSS) is an autoimmune, chronic inflammatory disease of unknown etiology characterized by progressive infiltration of mononuclear cells into salivary and lacrimal glands resulting in impairment of gland function. Reduced saliva flow might lead to severe unbalance in the oral microbiota. Such changes have been studied mainly with culture typically recovering only 65% of the bacteria present. Objective: To study the salivary microbiome of pSS patients. Methods: Bacteria of whole unstimulated saliva from nine patients with pSS and nine healthy controls were examined by high throughput sequencing of the hyper-variable region V1V2 of 16S rRNA using the 454 GS Junior system. Non-chimeric reads were aligned to a combined set of 16S rRNA reference sequences consisting of the Human Oral Microbiome Database (HOMD), HOMD extended (HOMDEXT), and Greengene Gold (GGG) datasets. Reads with greater than 98% sequence identity and 98% alignment length to the references were assigned with a species level taxonomy based on the highest sequence percent identity. To reveal significant differences between the microbiotas of control saliva and Sjögren’s saliva, a statistical method introduced in Metastats http://metastats.cbcb.umd.edu was used. Results: Saliva of pSS patients had a significantly higher frequency of Firmicutes compared to controls (p=0.001). Three other major phyla Synergistetes, SR1 and Spirochaetes were significantly depleted in pSS (p= 0.001, 0.011and 0.028, respectively). Additionally, we saw a nearly 30% decrease in the number of genera in pSS (76 vs 105). While Prevotella was equally abundant in both groups (20%), a 2-fold increase in pSS of Streptococcus (28% vs 15%) and Veillonella (26% vs 12%) was detected. Prevotella melaningenica was the major species in controls (12%) while Veillonella atypica and the Veillonella parvula group dominated in patient samples (13% and 13%).The scarcity in bacterial species in pSS compared to controls were also demonstrated by alpha and beta diversity and read abundance in a phylogenetic tree. Conclusions: While Firmicutes was significantly higher in pSS patients than in controls, Synergistetes, SR1and Spirochaetes were significantly lower. The number of bacterial genera and species was also lower. These data showed that microbial dysbiosis is another key characteristic of pSS whole saliva