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To study the colonization, growth and survival of microbial pathogens in microbial biofilms leading to a fuller understanding of this process in food processing environments and improved eradication methods.
Progress: Food surveillance programs linked to molecular typing of sequential bacterial isolates indicated the persistence of Listeria monocytogenes within food processing environments. Short contact time (1-24h) adherence assays have been developed and used to determine the adherence capabilities of persistent and non-persistent strains. Persistent strains tend to be more adherent than non-persistent strains. Two different systems, the Constant Depth Film Fermenter (CDFF) and the Annular Reactor (AR) have been used to study different aspects of the formation over a period of weeks of mature multispecies biofilms. The CDFF is particularly suited to the production of biofilms of different pre-determined thicknesses and was used to compare the susceptibility of planktonic and biofilm bacteria to increasing strengths of sodium hypochlorite. It was clearly shown that biofilm growth afforded significant protection against this commonly used sanitizer. The AR is suited to studies of the influence on biofilm formation of dynamic conditions such as hydraulic shear force, hydraulic retention time or nutrient fluctuation. Studies with the AR are at an early stage but useful data have been acquired on the effect of hydraulic shear forces and hydraulic retention time on the formation of monoculture and multispecies biofilms containing Listeria innocua.
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