BACKGROUND

is the most abundant member of the genus that inhabits the human large intestines. Evidences correlated the increase in abundance to inflammatory disorders, suggesting a pathobiont role.

OBJECTIVES

The aim of this study was to investigate the phylogenetic dynamics of in patients with irritable bowel syndrome (IBS), inflammatory bowel diseases (IBDs) and in healthy volunteers (CTRL).

DESIGN

A phylogenetic approach was used to characterize 64 16S rRNA sequences, selected from a metagenomic database of fecal and mucosal samples from 52 patients affected by IBD, 44 by IBS and 59 healthy.

METHODS

Phylogenetic reconstructions were carried out using the maximum likelihood (ML) and Bayesian methods.

RESULTS

Maximum likelihood phylogenetic tree applied onto reference and data sets, assigned all the reads to clade, in agreement with the taxonomic classification previously obtained. The longer mean genetic distances were observed for both the couples IBD and CTRL and IBD and IBS, respect to the distance between IBS and CTRL, for fecal samples. The intra-group mean genetic distance increased going from IBS to CTRLs to IBD, indicating elevated genetic variability within IBD of sequences. None clustering based on the tissue inflammation or on the disease status was evidenced, leading to infer that the variability seemed to not be influenced by concomitant diseases, disease phenotypes or tissue inflammation. Moreover, patients with IBS appeared colonized by different strains of . In IBS, a correlation between isolates and disease grading was observed.

CONCLUSION

The characterization of phylogeny is relevant to better understand the interactions between microbiota and pathophysiology of IBD and IBS, especially for future development of therapies based on microbes (e.g. probiotics and synbiotics), to restore the microbiota in these bowel diseases.