GROWTH OF LISTERIA-MONOCYTOGENES AT 10-DEGREES-C IN BIOFILMS WITH MICROORGANISMS ISOLATED FROM MEAT AND DAIRY PROCESSING ENVIRONMENTS

Listeria monocytogenes was able to grow in multispecies biofilms forme d on stainless steel at 10-degrees-C in the presence of bacteria isola ted from dairy and meat plant environments. Biofilm L. monocytogenes i ncreased more slowly in the presence of competing microflora than in m onoculture, but none of the eight competing isolates studied were able to completely exclude L. monocytogenes from the biofilm within 25 day s of incubation. Once a population of L. monocytogenes was established on the surface, it invariably increased in numbers. In biofilms conta ining a mixture of 4 competitive cultures, L. monocytogenes maintained itself at about 1% of the total population.