Evaluation of Virulence Gene Expression in Listeria monocytogenes Isolated from Various Foods Using RT-qPCR

• 1Aseel Ghazi Radhi 2 Fatema Shgeet Muftin 3Akram Haider Aliwi

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 The ability of Listeria monocytogenes to form biofilms on food contact surfaces poses significant challenges to food safety. This study investigated estimating the incidence of L. monocytogenes and the expression of virulence genes in diverse dietary matrices (raw milk, dairy products, meat products and fish products). The total number of samples was 100, with an equal number of samples from each dietary category (25 samples from each category). The total isolation rate of L. monocytogenes was 43%, and the highest frequency was found in fish items (60%), followed by meat (48%), raw milk (36%) and dairy products (28%). Molecular investigation showed that 74.4% and 55.8% of the isolates harbored actA and plcA genes, respectively. Reverse Transcription Quantitative Real-Time Polymerase Chain Reaction (RT-qPCR) analysis revealed significant differences in the expression of virulence genes between isolates from different food sources (P<0.001), with isolates from meat having the highest levels of expression for both genes . A negative correlation between Ct values and gene expression was detected, pointing out a higher transcriptional activity of the meat and fish isolates. The differences in expression and abundance of the genes identified are due to environmental barriers that can influence bacterial survival and regulation of virulence genes during the processing, storage and distribution of food. Although increased expression of virulence genes does not always mean that the bacteria are more harmful, the results of this study imply that contaminated foods of animal origin, especially meat and fish products, may be a serious public health problem. The inverse correlation between Ct values and relative gene expression reveals that the isolates obtained from meat and fish products had an elevated transcriptional activity of the actA and plcA genes. Factors influencing survival of bacteria, such as environmental challenges during food production, processing, storage and distribution, may also affect the regulation of genes involved in virulence, contributing to differences in prevalence and expression of genes. These results emphasize the importance of a multiplex molecular detection and quantitative gene expression analysis approach for better monitoring, characterization and risk assessment of Listeria monocytogenes in foods of animal origin

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