Proteins produced by Streptococcus species in the lower respiratory tract can modify antiviral responses against influenza virus in respiratory epithelial cells.

Seasonal influenza spreads during winter in temperate countries. Primary viral pneumoniae resulting from aggravation triggers acute respiratory distress syndrome, which is a serious respiratory disorder. We have identified a unique pattern of lung microbiota in patients with the syndrome. In this study, we hypothesized that the unique microbiota was also associated with primary influenza viral pneumoniae. Bacterial culture supernatants of Streptococcus oralis and Streptococcus mitis detected from the patients significantly increased viral replication (maximum 10-fold increase) in lung epithelial cells. Our results suggest that the lung environment microbiota is significantly involved in viral replication.