No association between the faecal microbiome and the presence of genuine irritable bowel syndrome symptoms in patients with quiescent inflammatory bowel disease

We aimed to assess the microbiome in 270 consecutive IBD patients who, using a combination of clinical diseaseactivity indices, the Rome III criteria for IBS and faecal calprotectin ?FC? ?using a cut-off of 250ug/g to define active mucosal inflammation?, were divided into four groups as follows: True IBS, quiescent disease, occult inflammation, active disease. Baseline demographic, disease related and psychological variables were compared between those with true IBS-type symptoms and the other three groups individually using a chi-squared test for categorical variables and an independent samples t-test for continuous variables. Due to multiple comparisons, a P value of 0.01 was considered statistically significant. Microbial DNA was extracted and analysed with next-generation sequencing of the V4 region of the 16S rRNA gene, on an Illumina MiSeq. Sequence reads were clustered into operational taxonomic units, which were then assigned genus-level taxonomy. The relative abundance of different taxa, as well as alpha ?within-sample? and beta ?between-sample? diversity was analysed using the Quantitative Insights Into Microbial Ecology ?QIIME? package.