INFLUENCE OF BACKGROUND MICROFLORA ON LISTERIA-MONOCYTOGENES ON MINIMALLY PROCESSED FRESH BROAD-LEAVED ENDIVE (CICHORIUM-ENDIVIA VAR LATIFOLIA)

Interactions between Listeria monocytogenes and the background microfl ora of endive leaves was studied by (i) testing the effect of disinfec ting endive leaves on the fate of L. monocytogenes, and (ii) challengi ng L. monocytogenes along with each of 10 strains of pseudomonads and Enterobacteriaceae isolated from endive leaves on both leaves of endiv e and in a model sterile medium based on an exudate of endive leaf. Th ere was a higher increase in the population of L. monocytogenes on end ive leaves with a background microflora reduced by a chemical disinfec tion. High numbers (10(6) to 10(7) CFU/g) of some strains reduced the growth of L. monocytogenes on endive. None of the 10 strains tested pr omoted the growth of L. monocytogenes. In the medium made of endive le af exudate, the 10 strains tested reduced the maximum growth of L. mon ocytogenes to extents that varied with the strains. A complex bacteria l population extracted from endive leaves completely inhibited the gro wth of L. monocytogenes in the medium.