Culture-independent evaluation of the appendix and rectum microbiomes in children with and without appendicitis.
OBJECTIVE
The function of the appendix is largely unknown, but its microbiota likely contributes to function. Alterations in microbiota may contribute to appendicitis, but conventional culture studies have not yielded conclusive information. We conducted a pilot, culture-independent 16S rRNA-based microbiota study of paired appendix and rectal samples.


METHODS
We collected appendix and rectal swabs from 21 children undergoing appendectomy, six with normal appendices and fifteen with appendicitis (nine perforated). After DNA extraction, we amplified and sequenced 16S rRNA genes and analyzed sequences using CLoVR. We identified organisms differing in relative abundance using ANOVA (p<0.05) by location (appendix vs. rectum), disease (appendicitis vs. normal), and disease severity (perforated vs. non-perforated).


RESULTS
We identified 290 taxa in the study's samples. Three taxa were significantly increased in normal appendices vs. normal rectal samples: Fusibacter (p = 0.009), Selenomonas (p = 0.026), and Peptostreptococcus (p = 0.049). Five taxa were increased in abundance in normal vs. diseased appendices: Paenibacillaceae (p = 0.005), Acidobacteriaceae GP4 (p = 0.019), Pseudonocardinae (p = 0.019), Bergeyella (p = 0.019) and Rhizobium (p = 0.045). Twelve taxa were increased in the appendices of appendicitis patients vs. normal appendix: Peptostreptococcus (p = 0.0003), Bilophila (p = 0.0004), Bulleidia (p = 0.012), Fusobacterium (p = 0.018), Parvimonas (p = 0.003), Mogibacterium (p = 0.012), Aminobacterium (p = 0.019), Proteus (p = 0.028), Actinomycineae (p = 0.028), Anaerovorax (p = 0.041), Anaerofilum (p = 0.045), Porphyromonas (p = 0.010). Five taxa were increased in appendices in patients with perforated vs. nonperforated appendicitis: Bulleidia (p = 0.004), Fusibacter (p = 0.005), Prevotella (p = 0.021), Porphyromonas (p = 0.030), Dialister (p = 0.035). Three taxa were increased in rectum samples of patients with appendicitis compared to the normal patients: Bulleidia (p = 0.034), Dialister (p = 0.003), and Porphyromonas (p = 0.026).


CONCLUSIONS
Specific taxa are more abundant in normal appendices compared to the rectum, suggesting that a distinctive appendix microbiota exists. Taxa with altered abundance in diseased and severely diseased (perforated) samples may contribute to appendicitis pathogenesis, and may provide microbial signatures in the rectum useful for guiding both treatment and diagnosis of appendicitis.
Sheikh Zayed Institute for Pediatric Surgical Innovation Children's National Medical Center, Washington DC, United States of America.
Hope T
HT
Jackson
Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
Emmanuel F
EF
Mongodin
Sheikh Zayed Institute for Pediatric Surgical Innovation Children's National Medical Center, Washington DC, United States of America.
Katherine P
KP
Davenport
Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
Claire M
CM
Fraser
Department of Pediatric Surgery, and the Sheikh Zayed Institute for Pediatric Surgical Innovation Children's National Medical Center, Washington DC, United States of America.
Anthony D
AD
Sandler
Center for Cancer and Immunology Research, Children's Research Institute, Children's National Medical Center, Washington DC, United States of America; Departments of Pediatrics and Microbiology, Immunology, and Tropical Medicine George Washington University, Washington DC, United States of America.
Steven L
SL
Zeichner
D000293:Adolescent; D001062:Appendectomy; D001064:Appendicitis / Q000382:microbiology*; D001065:Appendix / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005673:Fusobacterium / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D017861:Porphyromonas / Q000235:genetics / Q000302:isolation & purification; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012007:Rectum / Q000382:microbiology*; D012231:Rhizobium / Q000235:genetics / Q000302:isolation & purification
D012336:RNA, Ribosomal, 16S