Acute appendicitis in children is associated with an abundance of bacteria from the genus Fusobacteria

Matthew Rogers, Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America; Rachel Brower-Sinning, Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America; Brian Firek, Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America; Min Shi, Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America; Diana Zhong, Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America; Michael Morowitz, Division of Pediatric Surgery, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America

Although luminal obstruction has typically been viewed as the cause of appendicitis, recent evidence suggests that the disease results from invasion by specific pathogens. Recently, we reported an abundance of bacteria from the genus Fusobacterium in appendices of patients with acute appendicitis (AA). Here we expand our sample size to validate these preliminary findings.

We hypothesize that appendices of children with AA are enriched with Fusobacteria relative to children without appendicitis.

Appendix swabs were collected from children less than 18 years undergoing ileocecectomy for IBD (n=7), incidental appendectomy for reasons other than appendicitis (n=11), or appendectomy for AA (n=59). Appendicitis specimens were characterized as simple (n=39), perforated (n=12), or interval (n=8). After isolation of bacterial DNA, 16S ribosomal RNA gene sequences were sequenced on the Roche 454 and/or Illumina Miseq platforms. Computational analysis of the sequencing reads was performed with UPARSE and QIIME.

Species richness was similar, but taxonomic composition was markedly different between AA and non-appendicitis samples. As shown, swabs from AA patients harbored an increased abundance of members of the genus Fusobacterium relative to incidental and ileocecectomy samples (Wilcoxon rank-sum test p= 0.002). Conversely, Bacteroides was markedly depleted in appendicitis groups (p=0.015). We also identified several low abundance taxa (e.g. Campylobacter) that were present mainly in AA samples. Subgroup analysis of appendicitis specimens suggests an enrichment of Clostridiales in perforated AA specimens, suggesting a shift towards anaerobic metabolism in the progression from simple to perforated appendicitis.

Our results strongly support an association between AA and alterations in the appendiceal microbiome, specifically an increase in Fusobacterium and a decrease in Bacteroides. Follow up studies are required to determine how this knowledge can be leveraged to improve the diagnosis and/or treatment of patients with acute appendicitis.