ABSTRACT
Listeria monocytogenes is an intracellular, foodborne pathogen potentially lethal for humans and animals. Listeria species are widely distributed in nature but the disease is predominantly transmitted by the consumption of food contaminated by L. monocytogenes. Listeria cells are non-spore-forming Gram-positive rods, motile or non-motile. All Listeria species hydrolize esculin, a naturally occurring glucoside used to detect the enzyme β-glucosidase. Esculin is the most exploited substrate for β-glucosidase in culture media, but a range of synthetic glucosides is also available, resulting in colored end products. The psychrotrophic nature of L. monocytogenes is a problem for the food industry. The sources from which the pathogen reaches the factories include the workers, the air, the ingredients and raw material and the surfaces of the manufacturing environment. Many foods have been associated with the transmission of L. monocytogenes, including raw milk, inadequately pasteurized milk, chocolate milk, cheeses, sorbets, raw vegetables, meat, meat products, raw and smoked fish and seafood.
