WHEN ARE LISTERIA IN FOODS A HEALTH RISK

Infection with Listeria monocytogenes is a frequent occurrence, but the development of overt listeriosis is rare. Listeriosis is a serious illness that often results in death. The outcome is dependent on the strength of the host's defense system as well as on the bacterial virulence factors. Debilitated or immunocompromised persons and pregnant women are primarily at risk. Within the group of Listeria spp. basically only L. monocytogenes is dangerous, and even among the different strains of L. monocytogenes there are isolates with high virulence and others with low virulence. Currently, the degree of pathogenicity of an isolate cannot be determined in a routine laboratory. Improved methods to identify these virulence factors will help in the future to assess the real risk of Listeria found in foods.