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Pathogen reservoir hypothesis investigated by analyses of the adenotonsillar and middle ear microbiota
James Johnston1, Michael Hoggard2, Kristi Biswas1
1Department of Surgery, The University of Auckland, Auckland, New Zealand.
Introduction:
Adenotonsillar and middle ear diseases result in some of the most frequently performed operations in the pediatric population worldwide. The pathogen reservoir hypothesis (PRH) suggests that the adenoids act as a reservoir of bacteria which play a potential pathogenic role in otitis media. Evidence supporting this hypothesis is limited. This study sought to comprehensively determine and compare associations between the adenotonsillar and middle ear bacterial microbiota within individual patients via next-generation sequencing and microbial network analyses.
Methods:
Bacterial 16S rRNA gene-targeted amplicon sequencing was used to determine the bacterial composition of ten pediatric patients undergoing adenotonsillectomy and ventilation tube insertion for otitis media with effusion. At the time of surgery, swabs were taken from the adenoid surface, tonsil crypts and middle ear clefts (through the myringotomy incision).
Results:
The most abundant sequences within the bacterial community at genus level across all anatomical sites were Fusobacterium, Haemophilus, Neisseria, and Porphyromonas. There was an observable difference in the relative abundance of bacterial communities, with a higher proportion of Haemophilus and Moraxella in the adenoid when compared with the middle ear. Furthermore, only one module (consisting of 4 bacterial OTUs) from one patient was identified through microbial network analyses to be significantly associated between middle ear and adenoid. In addition, microbial network analysis revealed that the adenoid and tonsil microbiota share greater similarity than do the adenoid and middle ear.
Conclusion:
The results of this study suggest that the adenoid microenvironment does not correlate to the middle ear microenvironment. A future study at the species level, and over time, is required to further investigate whether the differing relationship between the microbiota of the adenoid and middle ear rejects the pathogen reservoir hypothesis.
Insights
The adenoids do not appear to be a reservoir for middle ear bacteria in children with otitis media. Further research is needed to explore the relationship between adenoid and middle ear microbiota.
Area of Science:
- Microbiology
- Otolaryngology
- Pediatrics
Background:
- Adenotonsillar and middle ear diseases are common in children.
- The pathogen reservoir hypothesis (PRH) posits adenoids harbor bacteria linked to otitis media.
- Limited evidence currently supports the PRH.
Purpose of the Study:
- To compare bacterial microbiota in adenoids, tonsils, and middle ear clefts of pediatric patients.
- To investigate associations between these microbial communities using next-generation sequencing and network analyses.
- To evaluate the pathogen reservoir hypothesis in pediatric otitis media.
Main Methods:
- 16S rRNA gene sequencing of bacterial samples from adenoids, tonsils, and middle ear clefts.
- Analysis of microbial communities in ten pediatric patients undergoing surgery for otitis media with effusion.
- Microbial network analysis to identify associations between anatomical sites.
Main Results:
- Fusobacterium, Haemophilus, Neisseria, and Porphyromonas were the most abundant genera.
- Adenoids showed a higher relative abundance of Haemophilus and Moraxella compared to the middle ear.
- Microbial network analysis revealed limited significant associations between adenoid and middle ear microbiota; adenoid and tonsil microbiota were more similar.
Conclusions:
- The adenoid microenvironment does not strongly correlate with the middle ear microenvironment in this cohort.
- Findings suggest the adenoid may not serve as a primary bacterial reservoir for middle ear infections.
- Further species-level and longitudinal studies are necessary to definitively test the pathogen reservoir hypothesis.
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