Listeria (L.) monocytogenes is a gram-positive, facultatively anaerobic, non-spore-forming rod. The natural habitat is probably decomposing plant matter, but L. monocytogenes can be isolated from many environmental sources since it is a mesophilic bacterium that grows well at room temperature, and continues to slowly replicate even at refrigerator temperatures. Listeriosis is of major veterinary importance in domestic ruminants. Among a number of disease conditions in listeriosis, encephalitis and uterine infection with abortion are the most common and serious ones (Low & Donachie, 2003). The survival in the environment and replication at low temperatures make L. monocytogenes a major and on eof the most lethal food-borne pathogens, particularly in dairy products (Ramaswamy et al., 2007). Contamination of cheese production facilities with milk from infected cows has caused numerous episodes of deadly human outbreaks of listeriosis with deaths of affected, typically immunocompromised individuals, and stillbirth or abortion.