*Review* **Upper Respiratory Tract Microbiome and Otitis Media Intertalk: Lessons from the Literature**

**Francesco Folino 1,\*, Luca Ruggiero 2, Pasquale Capaccio 3,4, Ilaria Coro 1,2, Stefano Aliberti 1,5, Lorenzo Drago 6, Paola Marchisio 1,2 and Sara Torretta 3,7**


Received: 19 July 2020; Accepted: 31 August 2020; Published: 2 September 2020

**Abstract:** Otitis media (OM) is one of the most common diseases occurring during childhood. Microbiological investigations concerning this topic have been primarily focused on the four classical otopathogens (*Streptococcus pneumoniae*, *Haemophilus influenzae*, *Moraxella catarrhalis* and *Streptococcus pyogenes*) mainly because most of the studies have been conducted with culture-dependent methods. In recent years, the introduction of culture-independent techniques has allowed high-throughput investigation of entire bacterial communities, leading to a better comprehension of the role of resident flora in health and disease. The upper respiratory tract (URT) is a region of major interest in otitis media pathogenesis, as it could serve as a source of pathogens for the middle ear (ME). Studies conducted with culture-independent methods in the URT and ME have provided novel insights on the pathogenesis of middle ear diseases through the identification of both possible new causative agents and of potential protective bacteria, showing that imbalances in bacterial communities could influence the natural history of otitis media in children. The aim of this review is to examine available evidence in microbiome research and otitis media in the pediatric age, with a focus on its different phenotypes: acute otitis media, otitis media with effusion and chronic suppurative otitis media.

**Keywords:** otitis media; microbiota; upper respiratory tract; adenoid; middle ear; microbiota axes
