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10. Indigenous Australians (IA) have a distinctive gut microbial profile compared to patients with inflammatory bowel disease (IBD) and non Indigenous controls

G. Iyngkaran1, S. Kang2, C. McSweeney2, S. Sivanesan1, M. Morrison2, F. Macrae1, 1Royal Melbourne Hospital, Department of Colorectal Medicine and Genetics, Parkville, 2CSIRO, Livestock Industries, Brisbane, Australia

Background

IBD is more common in developed nations and urban communities. The incidence of IBD in IA, who live traditional lifestyles in rural communities, is exceedingly rare. Australian health surveys of IA reveal a high level of childhood infections but no cases of IBD [1]. Similarly low rates of IBD were noted in Indigenous Canadians [2].

The aetiology of IBD is unknown but is thought to be due to a dysregulated immune response to an environmental trigger in a genetically susceptible host. An imbalance in the composition of gut microbiota, or “dysbiosis”, may be the trigger. Urbanisation may alter the exposure to environmental microorganisms and lead to dysbiosis. We hypothesise that IA have a distinct gut microbial profile, which may account for their low incidence of IBD.

Aim: To characterise the tissue adherent gut microbiota in IA, patients with Crohn's Disease (CD), Ulcerative Colitis (UC) and healthy controls with normal mucosa (HN).

 

Methods

Tissue samples from the terminal ileum and colon were obtained by colonoscopy from IA, HN, patients with CD and UC. Custom phylogenetic microarrays based on 16S rRNA gene sequences from gastrointestinal bacteria were employed to detect microbial diversity. Differences in relative abundance of microbial populations between groups were verified using Correspondance Analysis (CA) and Between group analysis (BGA) from ‘R package’ with ade4 and made4 library.

Results

63 patients were recruited (15 IA, 21 CD, 17 UC, 10 HN). There were significant differences (p = 0.001) in the gut microbial profiles between the groups (CD, UC, HN and IA) using BGA.

CD and UC groups had a high abundance of Firmicutes whereas the HN group had a high abundance of Bacteroidetes, in keeping with published data. The IA interestingly had a high abundance of Betaproteobacteria.

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Figure: Between Group Analysis (HN = Healthy, IA = Indigenous Australian, CD = Crohn's, UC = Ulcerative Colitis.

 

Conclusion

The IA have a distinct gut microbial profile compared to patients with CD, UC and HN which may be due to their traditional lifestyle. The low incidence of IBD in IA may be associated with their distinctive gut microbiota, which may have a protective effect or an ability to alter their immune response.

1. Australian Department of Health, (2008), Health and Welfare of Australia's Aboriginal and Torres Strait Islander Peoples 2008, Australian Department of Health.

2. Bernstein, C, (2006), The Epidemiology of IBD in Canada. A population based study. American Journal of Gastroenterology, 1559–68.