Mucosa-Associated Ileal Microbiota in New-Onset Pediatric Crohn's Disease

Background:The composition of the intestinal microbiome seems relevant to the pathogenesis of Crohn's disease (CD), with differences in both diversity and composition of the gut microbiota in patients with CD compared with healthy individuals. However, there are still conflicting reports on the importance of various bacterial taxa in the pathogenesis of CD. The aim of this study was to characterize the composition of mucosa-associated intestinal microbiota in newly diagnosed pediatric patients with CD.Methods:Mucosa-associated bacteria were identified from ileal biopsy specimens obtained at colonoscopy of 10 patients with either ileal or ileocolonic new-onset CD and 15 controls without mucosal inflammation. Microbial composition was performed by profiling the 16S rDNA V6 region using Illumina sequencing. Samples were analyzed for differences in alpha/beta diversity and also for differentially abundant taxa.Results:Alpha diversity did not differ between the controls and CD cases or between CD subjects with localized ileal disease compared with those with more extensive disease. Controls also did not clearly separate from patients with CD by principal coordinate analyses; however, 117 operational taxonomic units were found to be differentially abundant between the two groups. In particular, numerous operational taxonomic units associated with Faecalibacterium prausnitzii species were increased in children with CD.Conclusions:These findings contribute to emerging evidence regarding dysbiosis in pediatric CD, and provide additional evidence challenging the protective role of F. prausnitzii in CD.