ABSTRACT
The genus Listeria belongs to the phylum Firmicute, the order Bacillales, the class Bacilli, and the family Listeriaceae together with the genus Brochothrix. The Listeria is Gram-positive bacteria with low G+C content closely related to Bacillus, Clostridium, Enterococcus, Streptococcus, and Staphylococcus. The natural habitat of these bacteria is thought to be decomposing plant matter, in which they live as saprophytes. The potential primary sources for the introduction of L. monocytogenes pathogenic to humans into the food chain and food-processing plants include livestock and produce farms. Isolation of L. monocytogenes has been reported from cattle, silage, animal feeds, manure, and growing grass, among others [1, 2] as well as from soil, water, and vegetation of natural and urban environments [3, 4].
