Microbial profile of the appendix niche in acute appendicitis: a novel sampling approach

Relatively little is known about the microbial variations within the human appendix niche. To overcome this knowledge gap, we employed endoscopic retrograde appendicitis treatment (ERAT) technology to collect microbial samples from the appendix lumen, followed by shotgun metagenomic sequencing on participants with acute appendicitis without antibiotic treatment. Compared to the cecum and terminal ileum, the appendix had a higher abundance at the genus level of Sphingobium, Leptotrichia and Oribacterium, as well as a significant increase in species-level abundance of oral bacteria, including Streptococcus sanguinis, Streptococcus australis, Streptococcus sp. A12, Leptotrichia sp. oral taxon 215, Veillonella dispar, Veillonella infantium and Oribacterium sinus. Pearson correlation analysis showed that bacterial species abundant in the appendix, such as Acinetobacter johnsonii, Sphingobium yanoikuyae and Agrobacterium tumefaciens, had negative correlations with the top five most abundant Gene Ontology (GO) categories (molecular function, biological process and cellular component). Conversely, species underrepresented in the appendix, including Mogibacterium diversum, Streptococcus sanguinis, Megasphaera micronuciformis and Actinomyces graevenitzii, had significant positive correlations with these GO categories. Our results show that ERAT technology can be used to improve sampling and microbiome profiling in the appendix. Furthermore, this in-depth microbial characterization could inform clinicians during antibiotic prescription. However, further large sample size studies are required to validate these results.