Influence of Background Microflora on Listeria monocytogenes on Minimally Processed Fresh Broad-Leaved Endive (Cichorium endivia var. latifolia)

Abstract

Interactions between Listeria monocytogenes and the background microflora of endive leaves was studied by (i) testing the effect of disinfecting endive leaves on the fate of L. monocytogenes, and (ii) challenging L. monocytogenes along with each of 10 strains of pseudomonads and Enterobacteriaceae isolated from endive leaves on both leaves of endive and in a model sterile medium based on an exudate of endive leaf. There was a higher increase in the population of L. monocytogenes on endive leaves with a background microflora reduced by a chemical disinfection. High numbers (106 to 107 CFU/g) of some strains reduced the growth of L. monocytogenes on endive. None of the 10 strains tested promoted the growth of L. monocytogenes. In the medium made of endive leaf exudate, the 10 strains tested reduced the maximum growth of L. monocytogenes to extents that varied with the strains. A complex bacterial population extracted from endive leaves completely inhibited the growth of L. monocytogenes in the medium.