Growth of Listeria monocytogenes as a Biofilm on Various Food-Processing Surfaces

The objective of this research was to determine the ability of Listeria monocytogenes to grow as a biofilm on various food-processing surfaces including stainless steel, Teflon^®, nylon, and polyester floor sealant. Each of these surfaces was able to support biofilm formation when incubation was at 21°C in Trypticase soy broth (TSB). Biofilm formation was greatest on polyester floor sealant (40% of surface area covered after 7 days of incubation) and least on nylon (3% coverage). The use of chemically defined minimal medium resulted in a lack of biofilm formation on polyester floor sealant, and reduced biofilm levels on stainless steel. Biofilm formation was reduced with incubation at 10°C, but Teflon^® and stainless steel still allowed 23 to 24% coverage after incubation in TSB for 18 days. Biofilm growth of L. monocytogenes was sufficient to provide a substantial risk of this pathogen contaminating the food-processing plant environment if wet surfaces are not maintained in a sanitary condition.