Responses of Listeria monocytogenes to Different Stresses (pp. 405-444)
Authors: (Georgina Dowd, Colin Hill, and Cormac G.M. Gahan, Alimentary Pharmabiotic Centre, University College Cork, Ireland)
Abstract: Listeria monocytogenes is a Gram-positive foodborne pathogen capable of causing systemic infections leading to life-threatening meningitis in susceptible individuals or infection of the foetus in pregnant women. The pathogen normally resides in saprophytic environments but is capable of entering the food chain through zoonotic routes (via infection of livestock) or from environmental sources. The infectious cycle of L. monocytogenes therefore includes numerous sub-optimal environments within which the pathogen must survive and multiply. The pathogen has the ability to utilise molecular systems (the glutamate decarboxylase and arginine deiminase systems) to adapt to low pH conditions encountered both during food production and during passage through the stomach during infection. L. monocytogenes can resist high osmolarity in foods and within the small intestine through the uptake of specific osmolytes (glycine betaine and carnitine) using a variety of uptake systems. These and other mechanisms (bile salt hydrolase and bile exclusion system) are also involved directly in resistance to bile salts in the small intestine. The pathogen is also capable of adapting to conditions of heat shock and cold shock as well as conditions of low oxygen and reduced nutrients that may be encountered during food production or storage. Global transcriptomic and proteomic analyses have recently been applied to the understanding of these adaptive responses in L. monocytogenes. Here we describe the molecular response of L. monocytogenes to sub-optimal, stressful environments encountered at all stages during the infectious cycle.