Listeria Monocytogenes Research Paper

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Listeria monocytogenes is a gram-positive rod-shaped bacterium and facultative anaerobic that can grow under either anaerobic or aerobic conditions but do not form endospores. Among the six species of Listeria, only Listeria monocytogenes is the major human pathogen that causes disease in humans. It is a causative agent to cause listeriosis, a serious infection caused by ingesting the food contaminated with Listeria. The optimum temperature for growth is 30 to 37 degree Celsius, within this range, they multiply the best. Also, they can multiply better than all other bacteria at the refrigerator temperatures.

It was reported that about 2600 cases per year of severe invasive illness was caused by Listeria. This raised significant public health
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monocytogenes is a genus of Listeria and the species of pathogenic bacteria that cause infection listeriosis

Microscopically, listeria species appear as small, rod-shaped which are sometimes arranged in a short chains.

Intrinsic and Extrinsic factors affect the growth of pathogen
There are some intrinsic factors and extrinsic factors affect the growth of Listeria monocytogenes. For the intrinsic factors, the pH range for the growth of L. monocytogenes is 4.3 to 9.4. The survival times of Listeria monocytogenes would be shortened under an acidic condition.

Water activity is a measurement of energy status of water in a system. It is one of the most critical factors in determining the quality and safety of the foods because it affect the shelf life, safety, texture, flavor, and smell of foods. For gram-positive bacteria, the minimum water activity requirement is 0.9 or above, Listeria monocytogenes is 0.92. It can tolerate high sodium chloride levels and is able to grow in environments of up to 10% salt, to survive in 20 to 30% concentration. It is able to survive for some time in low water activity environments, also can survive in food drying process.

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