L. monocytogenes is a common bacterium in nature, it was only discovered to be a foodborne pathogen in the 1980's,despite being recognized as a human pathogen as early as 1926. Several food products have been linked with epidemics and sporadic cases of listeriosis, including meat, dairy, vegetable and fish products.Sporadic occurrence of the majority of cases makes tracing of vehicles of listeriosis difficult. Moreover, because the incubation period is long, there is often no food left for examination. Moreover L. monocytogenes is found in a variety of food products, thus hindering the linking of a specific product with cases of listeriosis. Listeria monocytogenes is a real problem for the ready-to eats meat industry.