How does Listeria monocytogenes combat acid conditions?

Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038-8598, USA.
Canadian Journal of Microbiology (Impact Factor: 1.22). 03/2013; 59(3):141-52. DOI: 10.1139/cjm-2012-0392
Source: PubMed


Listeria monocytogenes, a major foodborne pathogen, possesses a number of mechanisms that enable it to combat the challenges posed by acidic environments, such as that of acidic foods and the gastrointestinal tract. One mechanism employed by L. monocytogenes for survival at low pH is the adaptive acid tolerance response (ATR) in which a short adaptive period at a nonlethal pH induces metabolic changes that allow the organism to survive a lethal pH. Overcoming acid conditions by L. monocytogenes involves a variety of regulatory responses, including the LisRK 2-component regulatory system, the SOS response, components of the σ(B) regulon, changes in membrane fluidity, the F0F1-ATPase proton pump, and at least 2 enzymatic systems that regulate internal hydrogen ion concentration (glutamate decarboxylase and arginine deiminase). It is not clear if these mechanisms exert their protective effects separately or in concert, but it is probable that these mechanisms overlap. Studies using mutants indicate that the glutamate decarboxylase system can protect L. monocytogenes when the organism is present in acidic juices, yogurt, salad dressing, mayonnaise, and modified CO2 atmospheres. The glutamate decarboxylase system also has a role in protecting L. monocytogenes against the acidic environment of the stomach. There is a need to study other acid resistance mechanisms of L. monocytogenes to determine their effectiveness in protecting the organism in acidic foods or during transit through the acid stomach.

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    • "The species L. monocytogenes is widely studied in the developed world and is known as an enteroinvasive gastrointestinal pathogen (Barbuddhe and Chakraborty, 2009). There are no strains of L. monocytogenes with unique properties that lead to persistence (Carpentier and Cerf, 2011) and there are mechanisms that can protect the organism when present in acidic juices, yogurt, salad dressings, mayonnaise, and modified CO 2 atmospheres (Smith et al., 2013). Humans can become infected when contaminated food is ingested because the acidic stomach environment and its surface proteins (Bierne and Cossart, 2007) can help the organism to attach to the gut and multiply in the host's cell-cytosol (Pizarro-Cerdá and Cossart, 2009). "
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    ABSTRACT: Despite the world-wide reports of outbreaks of food-borne listeriosis, the occurrence of Listeria is still not widely reported in Nigeria. This is possibly due to lack of a large cold storage food chain and the absence of a comprehensive surveillance system for food-borne pathogens. Searches carried out on major databases revealed that Listeria has been reported in humans, animals, environment and food in Nigeria. In Nigeria, the organism has been reported in pregnant women and neonates while ruminants dominate reports of occurrence in animals. In food especially fish, L. monocytogenes is reported more than any other Listeria species. The organism has been isolated from water bodies and soils from different environments in Nigeria. However, all reports on the occurrence of Listeria spp. were based on classical serotyping, biochemical tests and dark colouration of media due to hydrolysis of aesculin with no emerging pattern of infection or dominant molecular serotype. There is an opportunity to utilize the current polymerase chain reaction based molecular techniques to characterize Listeria spp. so that accurate information on existing Listeria strains and sources of infection can be established in all regions in Nigeria.
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    • "Interestingly all elements of the GAD system are transcriptionally upregulated in Listeria during colonization of the GI tract (Archambaud et al., 2012). L. monocytogenes strains also possess an arginine deiminase (ADI) pathway and an agmantine (AgDI) deiminase system that contribute to pH homeostasis (Ryan et al., 2008; Smith et al., 2013). The ADI system is not present in the nonpathogenic species L. innocua. "
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