Our data showed that several antimicrobial peptides (S100A9), cytokines (IL-1β and TNF), and chemokines (CCL20, CXCL1, and CXCL2) that were associated to epithelial responses are also upregulated after the administration of the combination treatment in the post-flu superinfection model, suggesting that the epithelium is also an important flagellin-specific driving force in the lung damaged by viral and bacterial infections. Here, S100A9 is linked to bacterial infectious disease.