Pathogen Listeria Essay

Listeria is a genus containing several species. However, the most common and essential is the Listeria monocytogenes. Listeria monocytogenes is a Gram-positive bacillus, environmental and contaminates food (Nicki, Brian, & Stuart, 2010). It is a facultative intracellular bacteria that is known for causing central nervous systemic infections in humans and domestic animals (Drevets & Bronze, 2008). This pathogen can be found worldwide, and its outbreak has been associated with raw vegetables, soft cheeses, undercooked chicken, fish, and meat. It is the primary cause of Listeriosis, a gastrointestinal disease (Nicki, Brian, & Stuart, 2010; Drevets & Bronze, 2008). Listeria is a food-borne pathogen with a fecal-oral route of transmission. The bacteria grow rapidly at refrigerator temperatures which is why it is common in ready-to-eat foods, according to a food expert,  the risk of contamination increases in ready-to-eat food due to their centralized production and the need to store these foods in refrigerators favors the growth of Listeria (Waller, 2015). During the periods of production, transportation, and storage, the bacteria can multiply into numbers that exceed the threshold needed for infection.

Listeria monocytogenes is a facultative rod-like bacteria, which means it can survive in aerobic and anaerobic conditions. It is a short, non-spore forming rod. It is catalase-positive and has tumbling end-to-end motility at 22-28 degrees Celsius, but not a 37 degree Celsius; this is what differentiates it from diphtheroids that are also members of the skin’s normal flora (Brooks et al., 2010). Listeria’s virulence is different due too the various serotypes that it possesses, the most common serotypes in human are 1/2a. 1/2b, and 4b, and they make up 95 percent of the isolates from human (Brooks et al., 2010). The most common cause of outbreaks is the serotype 4b. Listeria monocytogenes enter into the through the gastrointestinal tract after consumption of contaminated food such as cheese and vegetables. The bacteria bind to the host cells through one of its several adhesin proteins, Ami, Fbp A, and flagellin proteins and this contributes to its virulence. The bacteria possess an internalin A which is cell wall surface protein that interacts with a receptor on the epithelial cells called E-cadherin. This promotes phagocytosis; the bacterium then gets enclosed in a phagolysosome which is then activated in low pH to produce listeriolysin O, this breaks the membrane of the phagolysosome allowing the listeriae to escape into the cell cytoplasm. The organisms proliferate allowing a surface protein to induce the “host cell actin polymerization” (Brooks et al., 2010, p. 180) propelling them to the cell membrane. This causes the formation of elongated protrusions called filopods. These filopods are engulfed by macrophages, adjacent epithelial cells, and hepatocytes releasing the listeria and begin the cycle over again. Listeria monocytogenes can move from cell to cell without exposure to antibodies, complement, or polymorphonuclear cells. Listeria grows on culture media of 5 percent blood agar on which it exhibits a small zone of hemolysis; it is catalase-positive, esculin hydrolysis positive, and motile. It does not produce gas but acid from utilizing various carbohydrates (Brooks et al., 2010). The motility, however, and production of hemolysin are what helps different Listeria from coryneform bacteria.

Listeriae produces siderophores and can obtain iron from transferrin. Therefore, iron serves as an important virulence factor. Immunity to Listeria monocytogenes is cell-mediated as shown due to its intracellular location as well as its association with immunocompromised individuals like pregnant women, the elderly, AIDS patients, and organ transplantation. Immunity can be transferred by sensitized lymphocytes and not antibodies.

In the perinatal stage of human development, there are two forms of human listeriosis, early-onset syndrome, and late-onset syndrome. The early onset syndrome called the granulomatosis infaseptica is when the infection occurs in utero due to the presence of the bacteria in the mother, Listeria can cross the placenta, although there is no person-person route of transmission. It is characterized by neonatal sepsis, pustular eruptions, and granulomatosis containing L.monocytogenes in various organs. The late-onset syndrome causes the development of meningitis which is often caused by the serotype 4b, and it has a significant mortality rate.

In adults, Listeria monocytogenes can cause meningoencephalitis, bacteremia, and focal infections. Meningoencephalitis and bacteremia occur mostly in immunocompromised patients. Febrile gastroenteritis is also common in patients after ingestion of contaminated food which occurs after an incubation period of 6-48 hours. Symptoms include fever, chills, headache, myalgia, abdominal pain, and diarrhea. It is mostly self-limiting, and laboratories do not take stool culture.

Listeriosis is diagnosed by isolating the organism in cultures of blood and spinal fluid. Antibacterial drugs are the therapy of choice for treating Listeriosis, ampicillin with erythromycin, or with intravenous trimethoprim-sulfamethoxazole. Cephalosporins and fluoroquinolones are not active against Listeria monocytogenes.

References

Brooks, G. F., Butel, J. S., Carroll, K. C., Mietzner, T. A., & Morse, S. A. (2013). Jawetz, Melnick, & Adelberg’s medical microbiology. The McGraw Hill Companies, Inc.

Drevets, D. A., & Bronze, M. S. (2008). Listeria monocytogenes: epidemiology, human disease, and mechanisms of brain invasion. FEMS Immunology & Medical Microbiology53(2), 151-165.

Nicki, R. C., Brian, R. W., & Stuart, H. R. (2010). Davidson’s principles and practice of medicine. Churchill Livingstone Elsevier.

Waller, P (2015). Everything You Need To Know About Listeria Monocytogenes.

The terms offer and acceptance. (2016, May 17). Retrieved from

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"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]

"The terms offer and acceptance." freeessays.club, 17 May 2016

[Accessed: March 28, 2024]
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