Abstract
Listeria monocytogenes is a Gram-positive facultative anaerobic bacterium that is responsible for the disease, listeriosis. It is particularly lethal in pregnant women, the fetus, the elderly and the immunocompromised. The pathogen survives and replicates over a wide range of temperatures (4 to 42 °C), pH, salt and oxygen concentrations. Because it can withstand various environments, L. monocytogenes is a major concern in food processing industries, especially in dairy products and ready-to-eat fruits, vegetables and deli meats. The environment in which the pathogen is exposed can influence the expression of virulence genes. For instance, studies have shown that variations in oxygen availability can impact resistance to stressors. Further investigation is needed to understand the essential genes required for the growth of L. monocytogenes in anaerobic conditions. Therefore, the purpose of this review is to highlight the data on L. monocytogenes under known environmental stresses in anaerobic environments and to focus on gaps in knowledge that may be advantageous to study in order to better understand the pathogenicity of the bacterium.
Highlights
Listeria monocytogenes was initially isolated in England in 1926 [1]
The ability of L. monocytogenes to cause listeriosis depends upon its ability to resist certain barriers/stressors encountered within the digestive tract, such as bile [11]
Listeria monocytogenes is successful in passing through three major barriers in the host: the intestines, the blood–brain barrier and the feto-placenta barrier
Summary
Listeria monocytogenes was initially isolated in England in 1926 [1]. It was first named Bacterium monocytogenes after fatalities occurred in many rabbits due to increased monocytes in the blood. The bacterium has been isolated from food processing plants, animal feces and soil It is inactivated by cooking and pasteurization; if proper sanitation procedures are not practiced, the risk of infection to the public through food processing can lead to illnesses. Good manufacturing practices and food safety laws have helped reduce the incidence of listeriosis; approximately 1500 infections and 255 deaths still occur annually [4]. Those that are most susceptible to this pathogen are pregnant women, fetuses, the elderly and the immunocompromised. The survival of L. monocytogenes in the digestive tract of food animals and in environments near or on surfaces associated with food processing needs further investigation to gain more insight on how foodborne outbreaks involving this pathogen propagate. As cultivation under anaerobic conditions has been found to significantly influence the survival of this bacteria, this review attempts to highlight the defined metabolic pathways, physiological changes and pathogenesis under anaerobic conditions
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