The murine appendiceal microbiome is altered in spontaneous colitis and its pathological progression

Inflammatory bowel disease (comprising ulcerative colitis and Crohn's disease) is a multifactorial disease that is extensively associated with stool microbiome changes (dysbiosis). Appendicitis and appendectomy limits subsequent colitis, clinically, and in animal models. We wanted to examine how the appendiceal and stool microbiome fared in our spontaneous colitic Winnie (Muc2(-/-)) mice model.

Two C57BL/6 and 10 Winnie mice at ages 12 and 15 weeks were euthanized for stool and caecal patch samples. DNA was extracted using the QIAamp DNA Stool Mini Kit then the V1-V3 hypervariable region of the 16S rRNA gene was sequenced using the Roche/454 GS FLX + pyrosequencing instrument. A Galaxy metagenomic pipeline was used to define phyla and families at sequence similarity threshold of ≥ 80%.

Bacteriodetes was decreased in 15-week Winnie mice appendices compared to corresponding stool samples (P < 0.01). Proteobacteria was increased in appendices of Winnie mice compared to corresponding stool samples (P < 0.05). The Bacteroidetes family Rikenellaceae could be identified only in 15-week-old Winnie mice appendices. A higher quantity of Acetobacteraceae (Proteobacteria phylum) was present in 15-week Winnie mice when compared to 12-week Winnie mice (P < 0.01). Helicobacteraceae (Proteobacteria phylum), which is prominent in all Winnie mice, is absent in control mice.

The appendiceal dysbiosis observed in our Winnie mice is commensurate with, and adds to extant literature data. The presence of Helicobacteraceae (Proteobacteria) only in colitic Winnie mice (but not control mice) is consistent with reports of increased Helicobacter in IBD patients. Bacteroides (Bacteroidetes) decreases may be a reflection of reduced anti-inflammatory commensal species such as B. fragilis. Further research is warranted to expand and delineate the relationship between IBD and the appendix microbiome.