Listeria

Listeria species of pathogenic (disease-causing) bacteria can be found in moist environments, soil, water, decaying vegetation and animals, and can survive and even grow under refrigeration and other food preservation measures.

Bacteria of the genus Listeria are Gram-positive, facultatively anaerobic, non-spore forming rods and are common in the natural environment.

The genus currently contains six species, L. monocytogenes, L. innocua, L. welshimeri, L. seeligeri, L. ivanovii and L. grayi, and four subspecies. Four species have been implicated in cases of human illness, but L. monocytogenes is by far the most important and is the cause of most reported cases of human infection. The species is made up of at least 13 different serotypes, all of which can cause listeriosis, but the most commonly found in human infection is serotype 4b.

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