Inhibition of Listeria monocytogenes by resident biofilms present on wooden shelves used for cheese ripening

The purpose of the present study was to characterize the development of Listeria monocytogenes on wooden shelves used for cheese ripening. The fate of two L. monocytogenes strains was analysed over time as a function of the presence of a native biofilm, the farmhouse origin of cheeses, and the wooden shelves properties. In presence of a native microbial flora on the shelves, deposited populations of L. monocytogenes remained stable or even decreased by up to 2 log10(CFU/cm2) after 12 days of incubation at 15 °C in all tested conditions. By contrast, L. monocytogenes populations increased by up to 4 log10(CFU/cm2) when the resident biofilm was thermally inactivated, suggesting a microbial origin of the observed inhibitory effect. All together, our results suggest that the biocontrol of pathogens multiplication on wooden shelves by resident biofilms should be considered for the microbiological safety of traditional ripened cheeses