Klebsiella aerogenes 11E12 isolated from the salivary microbiota of patients with IBD. Klebsiella aerogenes strain:11E12

Intestinal colonization of bacteria of oral origin has been correlated with several negative health outcomes, including inflammatory bowel disease (IBD), however, the causal role of such ectopically colonized oral bacteria in the intestine remains unclear. Using gnotobiotic techniques, here we demonstrate that strains belonging to Klebsiella isolated from the salivary microbiota of patients with IBD are strong inducers of T helper 1 (TH1) cells when colonized in the gut. These strains are resistant to multiple antibiotics, tend to colonize when the intestine has a dysbiotic microbiota, and elicit a severe gut inflammation in the context of a genetically susceptible host, presumably through the production of innate immune ligands. Our findings suggest that the oral cavity may serve as a reservoir for potential intestinal pathobionts and that a sub-type of IBD may exist, in which bacteria of oral origin induce TH1 cells and contribute to the disease pathogenesis.