The upper respiratory tract microbiome and its role in human health: barrier function

The human respiratory tract is a complex system characterized by a series of niches colonized with specific microbial communities. Until recently, researchers were mostly interested in lung microbiomes associated with acute and chronic infections. The upper respiratory tract microbiota has gained attention during COVID-19 (COronaVIrus Disease 2019) pandemic because it was suspected to influence the course and the outcome of viral infections. Aim. In this two-part review (see part 1, Pul’monolog;iya. 2022; 32 (5): 745-754), we summarize current knowledge of the microbial communities at each upper respiratory tract location, considering the proposed barrier function of the respiratory microbiome. Conclusion. Based on the evidence presented in this review, we can see how the respiratory microbiome is involved in the pathogenesis of viral respiratory infections, including SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus 2).