AB0147 Faecal microbiota study identifies dysbiosis in ankylosing spondylitis patients. (12th June 2018) - Chen, Z.
Abstract : Background: Ankylosing spondylitis (AS), a prototype of spondyloarthritis (SpA), is a chronic inflammatory disorder with diverse clinical phenotypes. It is widely accepted that AS is genetically determined and trigger of environmental factors is common. Accumulating research have indicated that gut microbiota may play a role in the pathogenesis of AS. Objectives: We conduct this study to characterise and investigate differences in the gut microbiome between patients and healthy donors. Methods: 41 patients with AS fulfilled the modified New York criteria for AS and 19 healthy controls (HCs) were recruited in this study. Fresh faecal samples were collected and microbial DNA were extracted by faecal DNA extraction kit acoording to the manufacture's instruction. V4 hypervariable region of the 16S ribosomal RNA (16S rRNA)was amplified and sequenced on an IlluminaHiSeq2500 platform. The resulting sequencing data were analysed through an in-house bioinformatics pipeline, including removing the barcodes and primers, merging forward and reverse reads, filtering tags, removing chimaeras, clustering and annotation. The mean species diversity for each sample and the differentiation among those samples are captured by alpha and beta diversity, respectively. Principle Coordinate Analysis (PCoA) was performed to get principal coordinates and visualise from complex, multidimensional data. Results: 16S rRNA community profiling of the faecal sample yielded high sequencing depth, with quality-filtered and connexion to generate a mean number of Taxon_tag being 66398±5606 versus 63061±5474 in AS and HCs group respectively. The gut microbial communities were significantly different and more diverse in AS patients when compared with the HCs by calculating metrics (Chao1) of a diversity (p<0.001). PCoA analysis shown that gut microbiota was able to predicted samples to be AS or HCs. At phylum level, the profile of gut microbiota were dominated by Bacteroidetes (56.15% vs 53.31%), Proteobacteria (11.19% vs 9.97%) and Firmicutes (30.10% vs 34.22%) in both AS and HCs groups respectively. However, difference of distribution were appeared between two groups, such that Bacteroidetes and Proteobacteria were more common in AS group, while Firmicutes was more common in HCs group. At genus level, both group were dominated by Bacteroides and Prevotella-9 . Abundance of Prevotella-9 were great different between AS patients and HCs with relative abundance of 16.07% and 2.86%, respectively. Conclusions: These results suggested that faecal microbiota of patients with AS differed significantly from that of healthy controls. Further analysis and larger cohort replication will be helpful to identified specific microbial marker of AS. References: [1] van der Linden S, Valkenburg HA, Cats A. Evaluation of diagnostic criteria for ankylosing spondylitis. A proposal for modification of the New York criteria. Arthritis Rheum1984;27(4):361–68. [2] Chao A, Chazdon RL, Colwell RK, et al. Abundance-based similarity indices and their estimation when there are unseen species in samples. Biometrics2006;62(2):361–71. Disclosure of Interest: None declared