The adhesion of putative probiotic lactobacilli to cultured epithelial cells and porcine intestinal mucus

Abstract

To investigate the adhesion of lactobacilli and their subsequent competitive exclusion ability against pathogens. Four species of putative probiotic lactobacilli were studied for their adhesion abilities. First, the adhesion to Caco-2 cells was examined by light and electron microscopy. The four species were then labelled by [methyl-(3)H] thymidine and their adhesion to porcine intestinal mucus was determined by radioactivity. The tested lactobacilli showed best adhesion on ileal mucus compared with duodenal and jejunal mucus. Oxidative compound pre-treatment (NaIO(3) and NaIO(4)) dramatically decreased the adhesion of the lactobacilli to mucus. Pre-treating mucus with proteolytic enzymes (proteinase K and trypsin) resulted in the increase of adhesion in Lactobacillus serotype Reuteri I2021, but the results in the other species were variable. Lactobacillus serotype Fermentum I5007 showed greatest adhesion potential and exerted the best competitive exclusion against Salmonella and Escherichia. Adhesion ability in lactobacilli is species-specific. Lactobacilli with higher adhesion index have better competitive exclusion ability. This study suggests that there is a positive correlation between adhesion and competitive exclusion ability of lactobacilli. Additionally, the in vitro adhesion assay is a feasible way to screen unknown lactobacilli, potentially for future industrial applications.