Expression of virulence genes of Listeria monocytogenes in food

In the present study, the development of reverse transcription-quantitative polymerase chain reaction protocols for three virulence genes (plcA, iap and hly) and the sigB stress response gene that may be applied for the determination of the virulence gene expression of Listeria monocytogenes in situ was reported. When applied to L. monocytogenes strains of different origin (#3, isolated frommeat;NationalCollection of Type Cultures 10527, a collection strain; and #162, isolated from cheese) and to four different food matrices (fermented sausage, soft cheese, ultrahigh temperature milk and minced meat), stored at 4 and 12C, significant heterogeneity in their expression was recorded. By statistical analysis of the data, it was possible to determine a significant effect on the gene expression by the food matrix, especially for the strain #162. This work showed that environmental factors may influence the virulence expression of L. monocytogenes providing better insights to the physiology of the microorganism grown in foods.