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P743 Gut microbial gene richness is reduced in smokers with Crohn’s disease

J. Opstelten*1, J. Plassais2, S. van Mil3, B. Oldenburg1, A. Cervino2

1University Medical Centre Utrecht, Department of Gastroenterology and Hepatology, Utrecht, Netherlands, 2Enterome, Paris, France, 3University Medical Centre Utrecht, Centre for Molecular Medicine, Utrecht, Netherlands

Background

Smoking has a negative effect on Crohn’s disease (CD) patients, but the mechanisms underlying this association are unclear. We compared the gut microbiota composition of smoking with non-smoking CD patients using a full quantitative metagenomic approach.

Methods

Stool samples and clinical data were collected from current smokers and non-smokers with CD from France and the Netherlands, matched for country, gender, age, and body mass index. Faecal DNA was sequenced on an Illumina HiSeq 2 500. On average, 40 million paired-end reads were generated per sample. Gene richness and the Shannon index were computed to assess microbial diversity. Wilcoxon signed-rank tests for paired samples were performed to detect differences between the 2 groups, and p-values were adjusted using the Benjamini-Hochberg procedure.

Results

In total, 21 smoking and 21 non-smoking CD patients with a median Harvey–Bradshaw disease activity index of 1 (interquartile range 0–2) were included. As compared with non-smoking patients, gut microbial gene richness (p = 0.01), genus diversity (p = 0.01), and species diversity (p = 0.03) were decreased in smoking subjects. This was accompanied by a reduced relative abundance of the genera Enterorhabdus (p = 0.03) and Gordonibacter (p = 0.02). No significant differences on the species level were observed, although smokers had a decreased relative abundance of Faecalibacterium prausnitzii (p = 0.10).

Conclusion

Gut microbial richness and diversity are reduced in smokers with CD compared with non-smokers with CD. The microbial profile also appears to differ between both groups regarding the relative abundance of bacterial groups on the genus level. Future studies should evaluate whether intestinal microbes mediate the adverse effects of smoking in CD.