ABSTRACT
Consumption of contaminated food has raised the number of outbreaks of fatal foodborne illness in last four decades. In most of the cases, pathogenic bacterial contamination has played the eminent role in these epidemic outbreaks. Listeria monocytogenes, a ubiquitous, Gram-positive, intracellular pathogenic bacterium has emerged as a leading causative contaminant in most of the outbreaks of foodborne diseases. Foodborne listeriosis caused by L. monocytogenes is one of the severe diseases with 0.1 to 10 cases per one million people every year, depending on the country and regions of the world. Listeria species are widely present in nature, including soil, sewage, water, plant, silage and in the intestinal tract of domestic animals (cattle, goats and sheep), and in humans where food acts as a principal carrier of infection, transmitting the bacteria through unprocessed meat, fish, vegetables, unpasteurized milk, etc. Due to its highly adaptive nature and high rate of evolving efficacy, L. monocytogenes can survive in adverse environmental conditions, such as a wide range of pH and temperature, low water activity, and high salt concentrations. Several surface proteins, such as hemolysin (listeriolysin O), two distinct phospholipases, ActA, and several internalins, act as major virulence factors. The role of these proteins, along with the genes involved in the pathogenesis of L. monocytogenes, is discussed in this chapter.
