Abstract

Listeria monocytogenes is a food-borne bacterial pathogen that is able to grow at refrigeration temperatures and resist freezing. This organism frequently colonizes and proliferates on preserved food products despite exposure to stress conditions induced by low storage temperatures. To investigate microbial virulence genes expression associated with cold shock, RT-PCR (Reverse Transcript PCR) assays was applied inthree isolated strains L. monocytogenes and reference strain ATCC 19115. These included cDNAs for L. monocytogenes genes involved in previously described virulences genes (hlyA, iap, flaA, fri, fbp) who cold-adaptive response is flaA, cold shock response isfri, cell surface alterations were fbp, and flaA, and the general microbial stress response (σ^β) which contributed to such stress resistance. Transcription of virulence genes was significantly increased after cold and freezing stress of different virulence genes used in this study. Transcript level for the σ^β gene was significantly affected by the factor temperature. These findings therefore suggest important roles of virulence genes and σ^βfactor to controls L. monocytogenes organisms against stress conditions associated with low storage temperatures.

Key words: Listeria monocytogenes, cold stress, virulence, expression