Bioprotective Effect of CNCM I-4031 Against Growth and Virulence.

is a Gram-positive pathogen occurring in many refrigerated ready-to-eat foods. It is responsible for foodborne listeriosis, a rare but severe disease with a high mortality rate (20-30%). CNCM I-4031 has the capacity to prevent the growth of in contaminated peeled and cooked shrimp and in a chemically defined medium using a cell-to-cell contact-dependent mechanism. To characterize this inhibition further, the effect of was tested on a collection of 42 strains. All strains were inhibited but had different sensitivities. The effect of the initial concentration of the protective and the target bacteria revealed that the inhibition always occurred when had reached its maximum population density, whatever the initial concentration of the protective bacteria. Viewed by scanning electron microscopy, cell shape and surface appeared modified in co-culture with CNCM I-4031. Lastly, virulence, evaluated by a plaque-forming assay on the HT-29 cell line, was reduced after cell pre-treatment by the protective bacteria. In conclusion, the bioprotective effect of toward growth and virulence was demonstrated, and a hypothesis for the inhibition mechanism is put forward.