Lessons in the Use of Probiotics to Inhibit Listeria monocytogenes Colonization on  Wooden Cheese Aging Surfaces

Boiling effectively decontaminates wooden cheese aging boards but also destroys biofilms on the surface that may inhibit pathogens. We assessed the efficacy of pre-inoculating wooden cheese aging boards with probiotic bacteria to prevent Listeria monocytogenes colonization and assessed how prior boiling cycles affected the efficacy of the treatment. On three separate occasions, a commercial lactic acid bacteria (LAB) cocktail was applied to 30/40 wooden boards in three different mediums. The LAB was made into yogurt (n=10), mixed into a commercial autoclaved yogurt (n=10), and mixed in phosphate buffered saline (PBS) (n=10) while the control boards (n=10) were only treated with PBS. All 40 boards were inoculated with 5 log CFU of L. monocytogenes. Half of the boards in each treatment group had never been boiled while the other half had previously been boiled three times. Boards were incubated for three weeks at 11°C. The control boards had significantly lower colonization (P < 0.05) of L. monocytogenes than the probiotic-treated boards; they, however, had the lowest nutrients present. Boiling history did not increase subsequent L. monocytogenes colonization. It is crucial to consider growth stage, nutrient presence, and pre-pathogen exposure colonization time to employ probiotics as an anti-Listeria control strategy.