Adhering heat-killed human Lactobacillus acidophilus, strain LB, inhibits the process of pathogenicity of diarrhoeagenic bacteria in cultured human intestinal cells.

Heat-killed L. acidophilus, strain LB, was tested for its ability to adhere in vitro onto human enterocyte-like Caco-2 and muco-secreting HT29-MTX cells in culture. The heat-killed LB bacteria exhibited a high adhesive property. A diffuse pattern of adhesion was observed to the undifferentiated cells, the apical brush border of the enterocytic cells, and to the mucus layer that covered the surface of the mucus-secreting cells. The inhibitory effect of heat-killed LB organisms against the human intestinal Caco-2 cell-adhesion and cell-invasion by a large variety of diarrhoeagenic bacteria was investigated. The following dose-dependent inhibitions were obtained: (i) against the cell-association of enterotoxigenic, diffusely-adhering and enteropathogenic Escherichia coli, Listeria monocytogenes, Yersinia pseudotuberculosis, and Salmonella typhimurium; (ii) against the cell-invasion by enteropathogenic Escherichia coli, Yersinia pseudotuberculosis, Listeria monocytogenes and Salmonella typhimurium.