Lactobacillus acidophilus (strain LB) from the resident adult human gastrointestinal microflora exerts activity against brush border damage promoted by a diarrhoeagenic Escherichia coli in human enterocyte-like cells

Background and aims: The normal gastrointestinal microflora exerts a barrier effect against enteropathogens. The aim of this study was to examine whether lactobacilli, a minor genus of the resident gut microflora, exerts a protective effect against the cellular injuries promoted by the diarrhoeagenic Afa/Dr diffusely adhering Escherichia, coli (Afa/Dr DAEC) Cl 845 strain in human intestinal cells. Methods: Cultured human intestinal fully differentiated enterocyte-like Caco-2/TC7 cells were used. Antibacterial activity was examined by measuring the viability of the adhering C 1845 bacteria. The distribution of brush border associated cytoskeleton and functional proteins was examined by immunofluorescence labelling coupled to confocal laser scanning microscopy analysis. Results: The activity of Lactobacillus acidophilus strain LB isolated from the resident human gastrointestinal microflora was examined. A dose dependent decrease in viability of C 1845 bacteria was observed after both direct contact in vitro between the spent culture supernatant (LB-SCS) and the bacteria, and when the bacteria were adherent on Caco-2/TC7 cells. Protection against the C 1845 induced alterations in expression of F-actin, sucrose-isomaltase, dipeptidylpeptidase IV, alkaline phosphatase, and fructose transporter alterations was observed when the cells were exposed to LB-SCS. Conclusion: L acidophilus strain isolated from the resident adult human gastrointestinal microflora, together with its antimicrobial activity, exerts a protective effect against the brush border lesions promoted by the diarrhoeagenic Afa/Dr DAEC strain C1845.