Ear microbiome: future insights for external and middle ear diseases?

The term microbiome has been coined in 2001 to indicate microorganisms colonizing the human body. Most of these germs are symbiotic and only a few are pathogenetic and potentially harmful. In the present study, evidence in literature about the role of ear microbiome in the external and middle ear diseases has been reviewed. A literature search through English-language studies about “microbiome,” “external ear,” and “middle ear” has been performed. Seven relevant peer-reviewed studies, published in the last 10 years, met the inclusion criteria. Recent acquisitions by next-generation DNA Sequencing showed that Turicella otitidis, Alloiococcus otitidis, and Staphylococcus auricularis may play a significant role in the pathogenesis of childhood acute otitis media, while S. auricularis, Staphylococcus capitis/caprae, Corynebacterium otitidis, and A. otitidis are involved in external ear infections. Several microbes have been identified also in adults’ middle and external ear acute and chronic infections: Cutibacterium acnes and S. capitis/caprae, and numerous fungi species (such as Aspergillus sp., Candida albicans, etc.) in otitis media; Proteus spp., Escherichia coli, Acetinobacter, Clostridium difficile, and Corynebacterium striatum in malignant external otitis, as well as some fungi (such as Candida albicans, Candida glabrata, Aspergillus spp., etc.). Acidovorax sp., Actinomycetales, and other bacteria have also been detected in the middle ear of patients suffering from cholesteatoma. The evidence in literature about ear microbiome has been increasing in the recent years, allowing a better comprehension of the pathogenesis of external and middle ear diseases. These findings could possibly offer novel therapeutic insights in a near future.