IL-8 induction by the flagellin of motile diffusely adherent E. coli

What is it about?

Escherichia coli is an ordinary member of the normal colon flora. However, particular clones can cause diarrheal diseases: the diarrheagenic E. coli (DEC). Diffusely adherent E. coli (DAEC) can bind to epithelial cells and represent a putative sixth DEC class. Their role in diarrheal disease, however, has been controversial, because the organisms can be detected not only among diarrheal patients but healthy people. We want to solve the epidemiological discrepancies. Previously, we found that motile DAEC organisms isolated from diarrheal patients could induce a high amount of proinflammatory cytokine IL-8 from epithelial cells. In this study, we tried to elucidate how these DAEC clones could induce IL-8 and found that the flagella of organisms caused the inflammatory response via TLR5 of epithelial cells.

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Why is it important?

There have been no criteria to determine the diarrheagenicity of DAEC. If the bacteria were isolated from outbreak patients, it should be easy to state that the bacteria was implicated as the etiological agent. However, when we found the organisms from a sporadic diarrheal patient, it is very difficult for the clinicians to judge whether the bacteria were causative agents. We found that only motile DAEC could induce severe secretion of proinflammatory cytokine IL-8 from the infected epithelial cells. In addition to the colonization factor, afimbrial adhesive sheaths (Afa), the flagella could be an additional virulence factor in causing enteritis.

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