Ectopic colonization of oral bacteria in the intestine drives TH1 cell induction and inflammation

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Science  20 Oct 2017:
Vol. 358, Issue 6361, pp. 359-365
DOI: 10.1126/science.aan4526

Gut reasons to brush your teeth

Some gut conditions, such as inflammatory bowel disease (IBD), ulcerative colitis, and Crohn's disease (CD), are associated with imbalances in the gut microbe community. The causes of these intractable diseases have been difficult to discern. Atarashi et al. took samples from the mouths of IBD and CD patients and inoculated the extracted bacteria into germ-free mice (see the Perspective by Cao). Some of the inoculated mice showed strong proliferation of T helper 1 cells associated with the establishment of oral Klebsiella species in the colon. Klebsiella can be resistant to multiple antibiotics and are able to replace normal colon microbes after antibiotic therapy. Now we know that they probably originate from the mouth and could potentially contribute to bowel disease.

Science, this issue p. 359; see also p. 308


Intestinal colonization by bacteria of oral origin has been correlated with several negative health outcomes, including inflammatory bowel disease. However, a causal role of oral bacteria ectopically colonizing the intestine remains unclear. Using gnotobiotic techniques, we show that strains of Klebsiella spp. isolated from the salivary microbiota are strong inducers of T helper 1 (TH1) cells when they colonize in the gut. These Klebsiella strains are resistant to multiple antibiotics, tend to colonize when the intestinal microbiota is dysbiotic, and elicit a severe gut inflammation in the context of a genetically susceptible host. Our findings suggest that the oral cavity may serve as a reservoir for potential intestinal pathobionts that can exacerbate intestinal disease.

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