Ectopic colonization of oral bacteria in the intestine drives T _H 1 cell induction and inflammation

Abstract

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 <i>Klebsiella</i> spp. isolated from the salivary microbiota are strong inducers of T helper 1 (T_H1) cells when they colonize in the gut. These <i>Klebsiella</i> 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.