The Microbiome of the External and Middle Ear: A Comparison of Healthy and Chronically Diseased States

Abstract

Our objective is to identify trends in microbiome composition and diversity of the human outer and middle ear in the healthy state compared to chronic otitis externa (COE) and chronic suppurative otitis media (CSOM). Adults ear samples were obtained in clinic or operating room. Samples were analyzed by 16S rRNA gene sequencing. The relative abundance of bacterial taxa and microbial diversity was calculated. Twenty-seven subjects were recruited. In healthy outer ear samples, skin commensal genera Corynebacterium, Propionibacterium, and Staphylococcus were typically represented in healthy outer ear communities, with variable contribution of Turicella and Alloiococcus. COM sample compositions fell into several clusters dominated by different putative pathogens. No significant differences were found in microbiome richness or diversity between healthy and diseased groups. The relative abundance of Propionibacterium was significantly decreased in COE compared to healthy outer ear samples (p < 0.05). Propionibacteria are known to exhibit strain-specific behavior as both opportunistic pathogens and commensals, which convey colonization resistance against pathogens and downregulate host inflammation in skin disease; they may also play a protective role against ear infections.