ABSTRACT
Listeria monocytogenes is a facultative intracellular gram-positive bacterium capable of causing serious illness in humans and animals (Farber and Peterkin, 1991). Infection is commonly induced by means of contaminated food, and individuals at risk include pregnant women and newborn babies, the elderly, and the immunocompromised. The pathogen is widely distributed in the environment, where its primary habitat may be soil and decaying vegetation. It has the ability to grow at refrigeration temperatures and to tolerate a wide range of pH and osmolarity (Gray and Killinger, 1966). The psychrotrophic nature of L. monocytogenes has rendered it a major threat to the safety of cold-stored foods, especially dairy products, and several outbreaks of disease (listeriosis) have been traced to contaminated cold-stored products (Schuchat et al., 1991).
