High salinity and temperature contribute to Listeria monocytogenes persistence by inducing the VBNC state

Introduction: Foodborne listeriosis has a low case rate but high mortality, posing a public health concern. Listeria monocytogenes can contaminate food-processing and storage environments, compromising the food supply chain. L. monocytogenes adapts to stresses like nutrient deprivation, extreme temperatures, and high salinity. Understanding its persistence mechanisms, including the ability to enter a viable but non-culturable (VBNC) state, is essential. Discussion: Microscopy using the BacLight assay showed significantly higher counts of viable cells compared to culturable cells detected using TSA and PALCAM, indicating the presence of VBNC cells. At 37 ºC, no colonies were observed with the plating method, yet viable cell counts remained high (BacLight assay). Similarly, at 8 ºC, viable cells outnumbered culturable bacteria. However, the low metabolic activity of L. monocytogenes at this temperature makes it less likely to enter the VBNC state. These results highlight the environmental conditions that promote the VBNC state in L. monocytogenes, offering insights for improving long-term storage, sterilization, and control measures in food products. Additionally, the findings emphasize the limitations of current culture-based methods in detecting VBNC bacteria, underscoring the need for more advanced detection techniques. Conclusion: Prolonged exposure to nutrient deficiencies, and high NaCl concentrations and temperature can induce the VBNC state of L. monocytogenes. VBNC cells evade detection by standard growth- based monitoring methods, thus improved detection methods, such as molecular screening techniques, are needed.