Intestinal Dysbiosis in Collagenous Colitis

Background The etiology and pathogenesis of collagenous colitis (CC) are incompletely known. Similar to other inflammatory bowel diseases (IBD), an aberrant immune response to various unidentified luminal factors, particularly the intestinal microbiota, seems to play an important role. Aim We aimed to compare the microbiotic profile between patients with CC, ulcerative colitis (UC), Crohnu0027s disease (CD) and healthy controls (HC). Methods Fecal samples were collected from patients at the out-patient clinic; UC (n=32), CD (n=32) and CC (n=29). Healthy controls (n=29) were matched by sex and age (+/-5 years) to the CC group. DNA was extracted through the Arrow Stool DNA cartridge using the Arrow Instrument (NorDiag). The hypervariable V3-V4 regions of the 16S rRNA genes were amplified by PCR and analyzed using high-throughput 454 pyrosequencing (Roche). The sequence data was filtered from bad quality sequences, denoised using AmpliconNoise and taxonomically classified using the SILVA database. Alpha diversity was assessed by Shannonu0027s diversity index and beta diversity by a Bonferroni corrected ANOSIM analysis, using Bray Curtis metrics as distance index. Differences in operative taxonomic units (OTUs) between groups of patients were analyzed by Wilcoxonu0027s test, False discovery rate was applied to adjust for multiple comparisons. Results The dataset contained 349 963 sequences with an average of 2 869 sequences/sample. Three samples (2 CC and 1 UC) were excluded due to low number of sequences. There was no difference in Shannonu0027s diversity index between patients with CC and HC (p=0.54). Analysis of the beta diversity using ANOSIM showed that the CC group segregated from the HC with increasing taxonomic resolution, reaching significance at the highest taxonomic resolution when operative taxonomic unit data (OTU) were compared (p=0.03). Wilcoxonu0027s test was further used to identify which OTUs that contributed to this difference. We found that several OTUs belonging to the Ruminococcaceae family were underrepresented in the CC group compared with the controls. Similarly, the beta diversity of patients with CD differed significantly from the HC and segregated already at a phylum level (p=0.007). In addition, the CD cohort was characterized by a lower Shannonu0027s diversity index (pu003c0.001). The beta diversity of patients with UC did not significantly differ from the HC (p=0.08 p=1.0), but the UC cohort was characterized by a lower alpha diversity (p=0.02). Conclusion The fecal microbiotic profile of CC differs from HC and is characterized by a lower abundance of OTUs belonging to the Ruminococcaceae family. Intriguingly, underrepresentation of the Ruminococcaceae family has previously been associated with CD indicating that the microbiotic profile of CC share features with the profile of CD. 1.Morgan XC, Et. al. Genome Biol. 2012; 13(9): R79