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(R), nylon, and polyester floor sealant. Each of these surfaces was able to support biofilm formation when incubation was at 21 degrees 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 degrees C, but Teflon(R) 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.