Research Highlights

Intestinal inflammation can be triggered by some oral bacteria species

Published online 26 October 2017

Bacteria from the mouth can replace normal, gut microorganisms under some circumstances, potentially contributing to bowel disease.

Lakshini Mendis

The complex community of microorganisms in your gut, known as the gut microbiome, consists of more than tens of trillions of microorganisms that are important for physiological functions like digestion. Imbalances in the gut microbiome have been linked to various bowel diseases, like inflammatory bowel disease (IBD) and Crohn’s disease (CD).

Now, studies have found out that the gut microbiomes of IBD and CD patients are enriched with oral (salivary) microbes.1 Motivated by these findings, Koji Atarashi and colleagues, including Heba Said, from Mansoura University in Egypt, set out to determine whether the salivary microbes were associated with gut microbiome imbalances, and bowel diseases.

As well, the scientists had noticed that, recently, there has been a sharp rise in the incidences of diseases like IBD and CD in the Middle Eastern region. 

When the researchers transplanted saliva samples from patients with IBD and CD into germ-free mice, strains of a specific bacterial species, Klebsiella, triggered a strong T-cell immune response in some rodents. 

Klebsiella can be resistant to multiple antibiotics and is known to replace normal colon microorganisms, after antibiotic therapy or when the microbiome is impaired. 

Severe inflammation in the gut elicited by Klebsiella could ultimately cause bowel disease, the scientists conclude in a new research paper published in Science.2

Atarashi tells Nature Middle East that the specific elimination of oral-derived bacterial, like Klebsiella (using very narrow spectrum antibiotics or a phage) could be a potential therapeutic strategy to correct IBD. Another is the use a mixture of beneficial bacteria, which may also specifically kill or decolonize Klebsiella.


  1. Ghosh. S., et al. Inflammatory Bowel Disease: A Global Disease. Saudi Journal of Gastroenterology: Official Journal of the Saudi Gastroenterology Association. (2013). 
  2. Atarashi, K. et al. Ectopic colonization of oral bacteria in the intestine drives TH1 cell induction and inflammation. Science (2017).