The ability of Lactobacillus adhesin EF-Tu to interfere with pathogen adhesion

Abstract

Probiotic bacteria play an important role in preventing widespread colonization of enteropathogens in human gastrointestinal tract. Lactobacillus plantarum CS24.2, isolated from child fecal sample, and L. rhamnosus GG, a widely accepted commercial probiotic strain, were examined in vitro for their ability to inhibit the colonization of enteropathogenic Escherichia coli (EPEC) and Salmonella enterica serovar Typhi (S. Typhi) on human intestinal epithelial cell line (Caco-2). Different adhesion assays such as competitive inhibition, adhesion inhibition, and displacement were carried out for the assessment of antagonistic activity of probiotic bacteria toward adhesion of enteropathogens to Caco-2 cells. Both the probiotic bacteria were able to inhibit pathogen colonization between 30–90% under different assay conditions. The gene coding for the known Lactobacillus adhesion factor—elongation factor Tu (EF-Tu)—was amplified from L. plantarum CS24.2 and cloned into E. coli expression vector, pET30(a). The partially purified recombinant EF-Tu was able to inhibit 50% adhesion of L. plantarum CS24.2 to Caco-2 cells but there was no effect on L. rhamnosus GG adhesion under competitive inhibition assay. To investigate the functional role of lactobacilli EF-Tu in pathogen inhibition to Caco-2 cells, competitive adhesion assay was carried out and there was significant reduction in the adhesion of E. coli (35.3%) and S. Typhi (47.7%) to Caco-2 cells.