P842 Analysis of fungal microbiota dysbiosis in inflammatory bowel disease

Abstract

Abstract Background Inflammatory bowel disease（IBD）is chronic relapsing and remitting disease of the gastrointestinal tract. Although the precise aetiology and pathogenesis of IBD remains elusive, epidemiological data conclusively point to be attributed to an aberrant immune response against environmental factors such as the gut microbiota in a genetically susceptible host. The bacterial microbiota plays a major role in human physiology and pathogenesis of IBD. The Fungi are often ignored in studies. Although the role of fungi has been suggested in pathogenesis of IBD, the available data are scarce. The aim of our study was to analyse and compare the faecal fungal microbiota in patients with IBD and healthy subjects (HS). Methods Our study evaluated fungal composition of the faecal microbiota of 66 patients with CD and 38 patients with UC diagnosed in West China Hospital and 39 HS by ITS2 sequencing. The Qiime pipeline was used to assess composition and diversity. Using LEfSe observed differential fungal composition between subjects. Results The faecal fungal microbiota was dominated by two phyla, basidiomycetes and ascomycetes in both IBD and HS. We observed that fungal microbiota was skewed in IBD, with an decreased basidiomycota/ascomycota ratio, a decreased proportion of Aspergillus and Saccharomyces and an increased proportion of Exophiala. Polythrincium, clonostachys, Candida compared with HS. Using LEfSe, we observed several differential fungal composition in different subject. Exophial a (p = 0.02), Agaricales (p = 0.02)species were overrepresented in UC, whereas Bulleribasidiaceae (p = 0.01), Ustilaginaceae (p = 0.007), Ustilaginales (p = 0. 007),Ustilaginomycetes (p = 0.007)species were overrepresented in HS. We then directly compared the fungal composition between subgroup of CD and UC, we observed Eurotiales（p = 0.007）, Aspergillus（p = 0.025), Thermoascus（p = 0.04）species were overrepresented in UC-remission. Ascomycota (p = 0.008) and Didymellaceae (p = 0.02)species were associated with CD-remission, whereas Saccharomyces (p = 0.03) and Xylariaceae (p = 0.006) species were associated with CD-flare. There was no significant difference in fungal Alpha diversity between IBD and HS. Beta diversity analysis showed that one subgroup of IBD samples segregated from HS whereas another subgroup overlapped with HS. Conclusion There was no significant change in fungal diversity in IBD. However, we observed fungal composition was skewed with decreased basidiomycota/ascomycota ratio on phyla level, particularly in IBD-flare group. The fungal composition was dominated by Aspergillus and Saccharomyces in HS, while the proportion of Exophiala, Polythrincium, Clonostachys, Candida was increased in IBD on genus level.