Listeriosis is a serious bacterial disease caused by the Gram-positive, rod-shaped bacterium, Listeria monocytogenes. The bacterium is widely distributed in nature and can be found in soil, water and contaminated food. Animals and food products such as vegetables can become contaminated from these sources. Infection with Listeria usually results in gastroenteritis with symptoms ranging from mild to severe. However, in persons with weak immunity, Listeriosis can lead to meningitis. In pregnant women, Listeriosis may results in pregnancy loss along with meningitis of their infant.