Analysis of appendectomy samples identified dysbiosis in acute appendicitis.

Appendicitis is the most common cause of sudden-onset abdominal pain requiring surgery. Culture-independent techniques have revealed that the complex intestinal bacterial ecology is associated with various diseases. To evaluate differences in patient characteristics and gut microbiota distribution in patients with appendicitis, we enrolled 12 patients who underwent appendectomy for appendicitis (appendicitis group) and 13 patients who underwent ileocecal resection or right hemicolectomy for colon cancer (control group). Microbiota were analyzed using next-generation sequencing of surgical specimens from appendix swab samples collected postoperatively. Overall differences in the structure of the gut microbiota were evaluated using the α- and β-diversity indices, which were calculated using the weighted or unweighted UniFrac distance. Changes in the gut microbial distribution were taxonomically evaluated at the phylum and genus levels. The α-diversity of observed species was significantly different between patients with and without inflammation of the appendix. The appendiceal microbiome of patients with appendicitis exhibited the highest unweighted UniFrac distances. There were no significant differences at the phylum level. Ruminococcus (p=0.02) and f_erysipelotrichaceae_g_clostridium (p=0.005) were increased in the control group compared with the appendicitis group. This pilot study provides the first report of the correlation of the gut microbiota with the pathogenesis of appendicitis evaluated using mucus-origin sampling.