Abstract:
Commensal bacteria play a crucial role in maintaining gastrointestinal homeostasis, among other things through stimulation and modulation of the immune system. Of particular interest are the so-called probiotics, i.e. microorganisms, that have beneficial effects for the host. The object of this research was to investigate in vitro the effect of commensal bacterial strains on Yersinia enterocolitica pYV- infection of human epithelial cells and to identify the factor which mediates this effect of commensal bacteria. As a model for the proinflammatory response, the Interleukin-8 induction in HeLa-cells that is induced by the enteropathogen strain of Yersinia enterocolotica pYV- working through Invasin-/Integrin-signaling was chosen. The involved molecular mechanisms are already well characterised. The tested bacteria were commensal strains, isolated from faeces of healthy adults, which belong to the following categories: Lactobacillus, Bifidobacterium, Bacteroides and Streptococcus. With the exception of Streptococcus salivarius, a soluble bacterial factor of commensal bacteria significantly inhibited, the Y enterocolitica pYV- by coinfection, induced IL-8 secretion. Further investigations with FeCl3, proteinase K, lipid extraction and phospholipase C showed that the antiinflammatory factor is possibly a phospholipid of < 10kDa molecular weight.
In the case of S. salivarius, a membrane-bound factor inhibited the IL-8 secretion.