Acute appendicitis manifests as two microbiome state types with oral pathogens influencing severity

Area of Science:

• Microbiology
• Gastroenterology
• Surgical Pathology

Background:

• Acute appendicitis (AA) is a common surgical emergency with poorly understood etiopathogenesis.
• Evidence suggests AA may represent two distinct disease entities: complicated and uncomplicated.
• Current diagnostic methods lack precision in differentiating these subtypes.

Purpose of the Study:

• To investigate the appendiceal, rectal, and peritoneal microbiome in pediatric patients with AA.
• To determine if distinct microbial communities correlate with complicated versus uncomplicated appendicitis.
• To explore the potential of microbiome analysis for improved AA diagnosis and treatment.

Main Methods:

• Inter-domain amplicon and metagenome sequencing of samples from 60 children and adolescents with AA.
• Analysis of microbial composition and function in appendix, rectum, and peritoneum.
• Comparison of microbiome profiles between complicated and uncomplicated appendicitis cases.

Main Results:

• Appendiceal microbiome composition significantly differed based on AA severity, forming two distinct community state types.
• Complicated appendicitis showed expansion of oral pathogens, notably *Fusobacterium* spp., *Porphyromonas*, and *Parvimonas*.
• Uncomplicated appendicitis was characterized by gut-associated microbial communities.

Conclusions:

• Findings support the existence of two distinct types of acute appendicitis.
• Standard clinical and rectal microbiome analyses cannot reliably distinguish between complicated and uncomplicated AA.
• Advanced microbiome diagnostics may enhance non-surgical treatment strategies for uncomplicated appendicitis.