They are motile at 25° C, showing a characteristic ‘tumbling’ motility, but non-motile are 35°C. Colonies have a characteristic bluish-grey appearance, which changes to blue green when viewed by oblique light.
Listeria monocytogenes is a facultative intracellular pathogen capable of causing gastroenteritis and the severe invasive disease, listeriosis.
Taxonomically, the genus Listeria consists of six species (L. monocytogenes, L. ivanovii, L. seeligeri, L innocua, L. welshimeri and L. grayi) of which only Listeria monocytogenes is an opportunistic intracellular pathogen responsible for human listeriosis.
Listeria is isolated from a diverse number of environmental sources, including soil, water, effluents, a large variety of foods and the feces of animals.
It is widely recognized that human listeriosis is largely attributable to food borne transmission of the microorganism.
Listeriae are acquired primarily through the consumption of contaminated foods including soft cheese, raw milk, deli salads and ready to eat foods such as luncheon meats and frankfurters.
Listeria monocytogenes
