The intra- and extraluminal appendiceal microbiome in pediatric patients

Abstract

Intestinal microbiota is involved in metabolic processes and the pathophysiology of various gastrointestinal disorders. We aimed to characterize the microbiome of the appendix in acute pediatric appendicitis comparing extraluminal and intraluminal samples.Between January and June 2015, 29 children (3-17 years, mean age 10.7 ± 3.4 years, sex M:F = 2.6:1) undergoing laparoscopic appendectomy for acute appendicitis were prospectively included in the study. Samples for bacterial cultures (n = 29) and 16S ribosomal desoxyribonucleic acid (rDNA) sequencing (randomly chosen n = 16/29) were taken intracorporeally from the appendiceal surface before preparation ("extraluminal") and from the appendiceal lumen after removal ("intraluminal"). The degree of inflammation was histologically classified into catarrhal, phlegmonous, and gangrenous appendicitis.Seventeen bacterial species were cultivated in 28 of 29 intraluminal samples and 4 species were cultivated in 2 of 29 extraluminal samples. Using 16S rDNA sequencing, 267 species were detected in intraluminal but none in extraluminal samples. Abundance and diversity of detected species differed significantly between histological groups of acute appendicitis in bacterial cultures (P = .001), but not after 16S rDNA sequencing.The appendiceal microbiome showed a high diversity in acute pediatric appendicitis. The intraluminal microbial composition differed significantly depending on the degree of inflammation. As bacteria were rarely found extraluminally by culture and not at all by sequencing, the inflammation in acute appendicitis may start inside the appendix and spread transmurally.

Acute appendicitis is associated with appendiceal microbiome changes including elevatedCampylobacter jejunilevels

“…6 Schulin et al performed both culture and 16S rRNA sequencing of appendiceal samples, again from paediatric subjects, and identified 11 genera by culture, of which Escherichia showed the highest abundance, and 109 genera by 16S sequencing, of which Fusobacterium showed the highest abundance, with Porphyromonas and Parvimonas also identified. 8 We did not find significant differences in the levels of any of these taxa in appendicitis versus control tissues in our study, which may be due to the fact that we used adult subjects, or that we specifically compared inflamed appendicitis tissues to non-inflamed controls.…”

“…However, more recent research has focused on the potential roles of overgrowth of appendiceal microbes and/or infection with bacterial pathogens. [4][5][6][7][8][9] Since McBurney performed the first appendectomy in 1889, 10 surgery has remained the gold standard for treatment of acute appendicitis. However, the clinical diagnosis can be challenging, and many of the conditions within the differential diagnosis require other treatment strategies.…”

“…Earlier studies attempted to identify causative bacteria using culture-based techniques, 18 19 fluorescence in situ hybridisation, 4 and so on, several of which suggested potential links between Campylobacter species and appendicitis. [20][21][22] More recent studies examined the appendiceal microbiome using next-generation sequencing, [5][6][7][8][9] the majority using paediatric populations. [6][7][8] Consistent findings included increased abundance of phylum Fusobacteria, 7 genus Fusobacterium 6 and specific Fusobacterium spp 8 in subjects with appendicitis, as well as increases in genera typically associated with the oral cavity, such as Porphyromonas and Parvimonas.…”

“…[20][21][22] More recent studies examined the appendiceal microbiome using next-generation sequencing, [5][6][7][8][9] the majority using paediatric populations. [6][7][8] Consistent findings included increased abundance of phylum Fusobacteria, 7 genus Fusobacterium 6 and specific Fusobacterium spp 8 in subjects with appendicitis, as well as increases in genera typically associated with the oral cavity, such as Porphyromonas and Parvimonas. [6][7][8] In this study, we used 16S rRNA gene sequencing and quantitative PCR (qPCR) to compare the appendiceal microbiomes and examine the prevalence of Campylobacter species in the appendices of adult subjects with confirmed acute nonperforated appendicitis and control subjects with healthy appendices.…”

The Microbiome in Adult Acute Appendicitis

“…Several other paediatric studies of appendicitis suggest that Fusobacterium is associated with acute appendicitis (Salo et al, 2017;Schulin et al, 2017;Swidsinski et al, 2012;Zhong et al, 2014) . Salo et.al.…”