Researchers found that saliva K. pneumonia of IBD patients rapidly establishes colonization in mice’s intestines, triggering a strong inflammatory response (upregulates IFN-γ, TH1 in the lamina propria, raises epithelial TNF-α mRNA expression in the proximal colon, and significantly induces IL-17, IFN-γ and CD4+ T cells level) (Atarashi et al., 2017). This evidence concerns the gene IFNG and irritable bowel syndrome.