The transcriptional response of virulence genes in Listeria monocytogenes during inactivation by nisin

The influence of preservatives on the expression of the virulence genes in Listeria monocytogenes (L. monocytogenes) is significant in assessing their functions and effectiveness against pathogens. In this study, the transcriptional response of the virulence genes (inlA, prfA, plcA, and hlyA) in L. monocytogenes during inactivation by nisin was investigated at 37 °C and 4 °C. The expression of these virulence genes decreased rapidly and remained at a constant level when nisin was added both at 37 °C and 4 °C. The decrease in the expression of the virulence genes caused by nisin at 37 °C was higher than that at 4 °C; thus, the ability of nisin to inhibit virulence genes expression at 37 °C is more effective than that at 4 °C. Regarding the effect of the nisin concentration on transcriptional inhibition, 500 IU/mL nisin caused significantly lower expression of the virulence genes than 100 IU/mL nisin at both temperatures. With the cell count increasing after the early bactericidal activity of nisin, the expression of the virulence genes also began to increase. Interestingly, the expression of these virulence genes all responded uniformly to nisin of different concentrations at different temperatures. A comprehensive understanding of the transcriptional response of the virulence genes in L. monocytogenes during inactivation by nisin could contribute to the effective application of nisin in the food industry.

► The expression of virulence genes in Listeria monocytogenes by nisin was investigated. ► Primers with high specificity and efficiency were designed to detect virulence genes. ► Various treatments of nisin were all studied to get a comprehensive understanding.