Environment, microbiota and host factors in otitis media

Otitis media is one the most common bacterial infections in early childhood, as well as one of the most common causes of antibiotic use and surgical treatment in children: In Denmark, two out of three children experience at least one episode during childhood 5, while more than one in four children undergoes tympanostomy tube insertion in full anesthesia 3. This high burden of disease has previously been shown to be unevenly distributed, both globally and within different populations 6. Numerous risk factors play a part in this variability, including both modifiable and non-modifiable factors 7. Understanding the causal mechanisms behind these risk factors are of great interest, as it may open new possibilities of disease prevention independently of the risk factors themselves. As such, the overarching aim of this thesis is to elucidate the roles and interplay of some of the largest risk factors for otitis media, notably the environment, the human microbiota and host factors.
Three separate studies form the backbone of this thesis, all of them reliant on data collected from the COPSAC2010 cohort comprising 700 children. This data includes: Bacterial culturing and 16s rRNA gene amplicon sequencing of more than 1,800 hypopharyngeal and 2,600 fecal samples obtained from 1 week to 6 years of age; immune mediator assays of airway mucosal lining fluid sampled at 1 month of age; otitis media symptom diaries registered daily until 3 years of age; information on tympanostomy tube insertions in the first 3 years of life obtained from national registers; and last but not least, information on numerous risk factors obtained through interviews with the primary caregivers.