Antagonistic Activity of Potential Probiotic Lactobacilli Against the Ureolytic Pathogen Yersinia enterocolitica

Strains of Lactobacillus spp., isolated from sourdough and olive brines (seven strains), and three human isolates were screened for their antagonistic activity in coculture against the ureolytic pathogen Yersinia enterocolitica. A general reduction in the pathogen population was observed after 6 h when each Lactobacillus strain was cocultured with the pathogen at a ratio of 100:1 cfu ml-1, causing an almost complete inhibition of urease activity. Strains were also screened for their performances in in vitro tests such as adhesion ability to Caco- 2 cells, tolerance to low pH, bile salts, and simulated digestion, which enabled the differences between strains to be highlighted. Three strains, L. paracasei IMPC2.1 and L. plantarum ITM21B and ITM5BG, met the main criteria for selecting effective probiotics: the ability to inhibit the pathogen Y. enterocolitica and, consequently, its urease activity (ITM21B); survival of simulated digestion (ITM21B and IMPC2.1); strong adhesion ability to enterocytes and good survival at low pH and in the presence of bile salts (ITM5BG and IMPC2.1).