Biodiversity And Structural Composition Of Gut Microflora In Inflammatory Bowel Disease

Background & Objective: The pathogenesis of inflammatory bowel disease(IBD) remains unclear so far. It has been reported that dysbiosis of gut microflora might be related to the occurrence and development of IBD. This study aims to identify the dysbacteriosis in IBD morbid state and seek for the specific gut bacteria which have significant association with IBD.Methods: Denaturing gel gradient electrophoresis(DGGE) and(or) high-throughput sequencing techniques were applied based on the 16 S r DNA sequences, to analyze the faecal bacterial biodiversity and structural composition in IBD model mice, which were induced by dextran sulfate sodium(DSS), and in IBD patients with different clinical phenotypes.Results: Species richness indices and Shannon diversity indices were found with no significant differences in acute and chronic DSS-colitis mice’s faecal bacteria compared with healthy ones(p>0.05). The similarity among the groups was lower than it within the groups, according to Dice coefficients. Both faecal bacterial richness and diversity in patients with all IBD phenotypes, including active and paracmastic Crohn’s disease(CD) and ulcerative colitis(UC), were markedly lower than that in healthy controls(all p values < 0.05), and obvious individual variations were observed among all cases. The major phyla in IBD patients and healthy people consisted of Bacteroidetes, Firmicutes and Proteobacteria. Compared with healthy controls, the remarkable changes( p<0.05) of faecal bacterial composition in IBD patients included: on phylum level, Firmicutes and Bacteroidetes were separately decreased in CD and active UC. Proteobacteria were increased in all IBD phenotypes. On genus level, Ruminococcaceae and Bacteroides were decreased in CD and active UC, respectively. Faecalibacterium were decreased in both CD and paracmastic UC. All IBD phenotypes got a significant increase in Streptococcus, Enterococcus, Escherichia-Shigella and a remarkable decrease in Pseudobutyrivibrio and Alistipes.Conclusions: This present study analyzed the differences of faecal bacteria in IBD model mice, IBD patients and healthy controls, and observed the changes of gut microflora under the IBD morbid states. We identified that both bacterial richness and biodiversity were significantly decreased in IBD patients and dysbacteriosis did exist.