The increased interest in the microbiota of the human intestine is associated with her involvement in initiating the initial stages of the disease and the occurrence of chronic forms of complications. Normally, the intestinal epithelium fulfills the barrier function, which allows to control the permeability of bacteria and their metabolites, thanks to the work of a whole complex of mechanisms that impede free transport: tight-contact proteins and a thick layer of mucus on the epithelium surface. Violation of the barrier function leads to translocation of bacteria and pathogenicity factors into the systemic bloodstream, which can lead to multiple organ failure. Currently available data on the effect of pathogenicity factors on the translocation of living bacteria does not allow to evaluate the effect of endotoxin on the permeability of the mucous membrane with the increased role of Gram-negative bacteria on the development of intestinal dysfunctions. In this connection, the aim of the study was to analyze the detection of morphological changes in the mucous membrane of the small intestine of rats with simultaneous introduction of endotoxin into the lumen of the intestine in combination with the probiotic bacteria Lactobacillus plantarum 8 PA-3 and Escherichia coli M17. The aim of the study was to identify morphological changes in the mucosa of the jejunum of rats with simultaneous introduction of endotoxin in the intestinal lumen in a complex with probiotic bacteria. Materials and methods. The study was carried out on male Wistar rats. Probiotic bacteria Lactobacillus plantarum 8-PA3 and E.coli M17 (108 CFU/ml) and lipopolysaccharide (LPS) (20 mg/ml) were injected into the lumen of the jejunum of rats. The results of the exposure were assessed using histological methods. Results. Analysis of histological specimens showed that increasing the concentration of LPS and adding to the lumen of the jejunum of rats a bacterial suspension of E.coli M17 resulted in an increase in the secretion of mucus by goblet cells and increased secretion of lysozyme by Paneth cells. In the presence of lactobacilli, this phenomenon is less pronounced. Conclusions. It was found the neutralization effect of the LPS, during co-introduction of LPS with E. coli M17 and L.plantarum 8RA-3 into the lumen, however, the involved mechanisms are different.