Biofilm formation in various conditions is not a key factor of persistence potential if Listeria monocytogenes in food-processing environment

In this study, a hypothesis was tested that biofilm formation ability, or ability to form biofilm in specific conditions, is responsible for persistence of Listeria monocytogenes in food processing environment. Thirty-three L. monocytogenes strains isolated from food-processing environment and food products were tested for biofilm-forming ability in various conditions. Biofilm-forming ability was tested with exponential-phase cultures at 20 °C, 37 °C and 40 °C, with stationaryphase cultures at 20 °C, 37 °C and 40 °C, with cultures grown in limited-nutrient conditions and with cultures grown in high-salt conditions at 4 °C. Biofilm was formed in 96-well polystyrene plates and quantified by the method based on staining with crystal violet. The results showed that biofilm-forming ability of L. monocytogenes strains was variable, individual strains exhibiting different relative biofilm-forming ability in various conditions. No statistically significant differences between the groups of persistent and sporadic strains in biofilm-forming ability in any of the conditions were determined. Based on our results, biofilm-forming ability of L. monocytogenes is not a key factor that determines its persistence potential in food-processing environment