Evaluation of the microbiome in children’s appendicitis

The role of the microbiome has been widely discussed in the etiology of appendicitis. The primary aim was to evaluate the microbiome in the normal appendix and in appendicitis specifically divided into the three clinically and histopathologically defined grades of inflammation. Secondary aims were to examine whether there were any microbiome differences between proximal and distal appendices, and relate the microbiome with histopathological findings.

A prospective pilot study was conducted of children undergoing appendectomy for appendicitis. The diagnosis was based on histopathological analysis. Children with incidental appendectomy were used as controls. The proximal and distal mucosa from the appendices were analyzed with 16S rRNA gene sequencing.

A total of 22 children, 3 controls and 19 appendicitis patients; 11 phlegmonous, 4 gangrenous, and 4 perforated appendices, were prospectively included. The amount of Fusobacterium increased and Bacteroides decreased in phlegmonous and perforated appendicitis compared to controls, but statistical significance was not reached, and this pattern was not seen in gangrenous appendicitis. No relation could be seen between different bacteria and the grade of inflammation, and there was a wide variation of abundances at phylum, genus, and species level within every specific group of patients. Further, no significant differences could be detected when comparing the microbiome in proximal and distal mucosa, which may be because the study was underpowered. A trend with more abundance of Fusobacteria in the distal mucosa was seen in appendicitis patients with obstruction (25 and 13 %, respectively, p = 0.06).

The pattern of microbiome differed not only between groups, but also within groups. However, no statistically significant differences could be found in the microbiome between groups or clinical conditions. No correlation between a specific bacteria and grade of inflammation was found. In the vast majority of cases of appendicitis, changes in microbiome do not seem to be the primary event. Since there seem to be differences in microbiome patterns depending on the sample site, the exact localization of biopsy sampling must be described in future studies.