Listeria monocytogenes (L. monocytogenes) is a bacterium which is ubiquitous in the environment and the causative agent of listeriosis, a major food-borne disease affecting humans and livestock. In humans, pregnant woman, the elderly, and immuno-compromised people are affected while the high rate of fatality of 20% to 30% makes L. monocytogenes a significant cause of food-borne related human mortality. In sheep and cattle L. monocytogenes is a major cause of miscarriage and encephalomyelitis resulting in welfare issues and significant economic losses. We have isolated a number of strains of L. monocytogenes from a variety of sources, with different pathogenic potential (1). The DNA from these isolates have been sequenced and we are carrying out bioinformatic analysis to determine the presence or absence of virulence factors associated with disease. However, in silico predictions alone cannot fully define the virulence of an organism. The current project will determine the virulence of different strains of L. monocytogenes using Galleria mellonella, a well characterised invertebrate model of virulence (2). If it is found that environmental strains demonstrate only limited disease causing potential then this will provide the industry with extra tools for managing risk and developing appropriate control mechanisms.