Listeria monocytogenes (commonly known as listeria) is a bacterium that is widespread in the environment. It is found in soil, vegetation, water, sewage and the feces of animals and humans. Listeria can cause Listeriosis, a serious but rare illness that in certain cases can lead to brain infection and even death. The elderly, newborns, pregnant women and those who have a weakened immune system are most susceptible to developing Listeriosis.