Competition ofLactobacillus paracaseiwithSalmonella entericafor Adhesion to Caco-2 Cells

[摘要] Competition of commensal and probiotic bacteria with pathogens for adhesion and colonization is one of the important protective mechanisms of gastrointestinal tract. In this study, we examined the ability ofLactobacillus paracaseito inhibit the adhesion of pathogenicSalmonella entericato human colon adenocarcinoma Caco-2 cells. Caco-2 cells were grown for 6 or 21 days to obtain nondifferentiated or well-differentiated cells, respectively. In adhesion experiments, bacteria were added to the cells for 2 or 4 hours. The number of attached bacteria was expressed as colony-forming units (CFUs), Caco-2 cells were counted in hematocytometer. Both bacterial strains used adhered better to well-differentiated than to nondifferentiated Caco-2 cells, however, the amount ofSalmonellaadhered to Caco-2 after 2 hours of contact was 12-fold higher in comparison toL.paracaseiand almost 27-fold higher after 4 hours of contact. Two types of experiments were done: coincubation (both bacteria were added to Caco-2 cells simultaneously), and preincubation (L.paracaseiwas incubated with Caco-2 cells first, and thenS.entericawas added). In coincubation experiment, the presence ofL.paracaseidecreasedS.entericaadhesion by 4-fold and in preincubation experiment even 7-fold. Generally,Lactobacillusspent culture supernatants (SCSs) acted weaker as inhibitors ofSalmonellaadhesion in comparison to the wholeL.paracaseiculture in coincubation experiment. In conclusion, the displacement of pathogens by lactic acid bacteria and its secretions showed here depends on the time of bacteria-epithelial cell contact, and also on the stage of Caco-2 differentiation.

[学科分类] 基础医学