Characterizing the otologic microbiota to prevent recurrent otitis
Bacteria in the nasopharyngeal microbiota could offer protection against recurrent acute otitis media in children and open the way to targeted probiotic treatments.
Recurrent acute otitis media (AOM) is common in early childhood and its treatment with antibiotics has limitations: antibiotics are not always effective, encounter resistance, and the insertion of tympanostomy tubes (or grommets) sometimes needs to be repeated. The probiotic route has shown disparate results to date. A detailed analysis of the microbiota of the middle ear and nasopharynx in children with recurrent AOM to highlight potential protective strains was lacking. This has now been performed by an Australian team for the first time.
Two potentially protective genera
As the middle ear is difficult to access, the researchers took advantage of the insertion of tympanostomy tubes in 93 children with recurrent AOM to take samples (fluid and bacteria from the middle ear, the auditory canal and the nasopharynx). Nasopharyngeal samples were taken from control children going to the nursery or having a sibling under five years of age (two risk factors for recurrent AOM). Three genera were more abundant in healthy children: Corynebacterium and Dolosigranulum, associated in previous studies with a lower risk of AOM, and to a lesser extent Moraxella (similar to M. lincolnii). Two elements known to affect the number of Corynebacterium and Dolosigranulum were also present in patients with AOM: a shorter period of maternal breastfeeding and recent administration of antibiotics to the child. This suggests that the maintenance of a healthy flora could prevent the risk of relapse.
Otopathogens or healthy residents?
The second objective of this study was the identification of new otopathogens other than those usually encountered: Haemophilus influenzae (NTHi*), Streptococcus pneumoniae and Moraxella catarrhalis. They colonize and infect the middle ear by travelling from the nasopharynx through the Eustachian tube. Other bacteria were found in greater abundance in samples from sick children: Alloiococcus (the predominant genus), Staphylococcus and Turicella. However, the authors do not exclude the possibility that these bacteria also belong to the commensal flora. Another result was that the nasopharyngeal microbiota of the sick children was more diversified than that of controls. It hosts the genera Gemella and Neisseria in particular. Do these bacteria have a proven role in rAOM** or are they the consequence of a dysbiosis? According to the authors, it is unlikely that they are otopathogens since they do not seem to colonize the middle ear. This study lays the foundation for more in-depth studies of the beneficial or harmful role of these various bacteria. This might lead to consider additional therapies based on probiotics capable of improving the quality of life of the children affected.
*NTHi*: Nontypeable (or unencapsulated) Haemophilus influenzae
**rAOM: recurrent acute otitis media
R Lappan et al. A microbiome case-control study of recurrent acute otitis media identified potentially protective bacterial genera. BMC Microbiology 2018; 18:13