Alloiococcus otitidis May Play Large Role in Otits Media with Effusion

by Samara E. Kuehne •

Does a correlation exist between the middle ear and adenoid microbiota in children with otitis media with effusion (OME)?

BOTTOM LINE
The microbiome of the middle ear in OME is diverse with both aerobic and anaerobic bacteria represented. AO is found in high abundance and may play a major role in the pathogenesis of OME, especially unilateral effusions, and displays an antagonistic relationship with Haemophilus. Furthermore, dissimilarities between the local microbiota of the adenoid and the middle ear were demonstrated in this study population, suggesting that the microenvironment of the middle ear plays a greater role in the composition of the microbiota than the potential bacterial seeding from the adenoid pad to the middle ear in children with OME.

Background: OME is the most common cause of hearing loss in childhood. The pathogenesis of OME remains unclear, although the eustachian tube (ET) is thought to play a central role. It has been suggested that the ET’s short length, horizontal position, and reduced rigidity in the pediatric population may permit the reflux of naso- and oropharyngeal microbes into the middle ear cavity, explaining the higher incidence of OME in children when compared with adults.

Traditional culture-based techniques have isolated Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis as the most common pathogens in OME, and the advancement of culture-independent techniques such as 16S rRNA pyrosequencing has identified the pathogen Alloiococcus otitidis (AO) as a potential pathogen; it has been isolated from middle ear aspirates with increasing frequency in the last decade. The aim of this study was to use culture-independent techniques to compare the local microbial population of the adenoids in patients with and without OME and test the hypothesis that this region acts as a bacterial reservoir, predisposing patients to OME.

Study design: Prospective, controlled study.

Synopsis: Middle ear aspirates adenoid pad swabs were collected from 23 children undergoing ventilation tube insertion. Adenoid swabs from patients without ear disease were controls. Samples were analyzed using 16S rRNA sequencing on the Illumina MiSeq platform.

Thirty-five middle ear samples were collected. The middle ear effusion microbiota was dominated by Alloiococcus otitidis (23% mean relative abundance), Haemophilus (22%), Moraxella (5%), and Streptococcus (5%). Alloiococcus shared an inverse correlation with Haemophilus (P=0.049) and was found in greater relative abundance in unilateral effusion (P=0.004). The microbiota of bilateral effusions from the same patient were similar (P < .001). However, the otitis media with effusion microbiota were found to be dissimilar to that of the adenoid (P=0.01), whereas the adenoid microbiota of otitis media with effusion and control patients were similar (P>0.05) (permutational multivariate analysis of the variance).