Listeria monocytogenes wiki

Listeria monocytogenes [L. monocytogenes] is a species of pathogenic [disease-causing] bacteria that can be found in moist environments, soil, water, decaying vegetation and animals, and can survive and even grow under refrigeration and other food preservation measures. When people eat food contaminated with L. monocytogenes, they may develop a disease called listeriosis.

L. monocytogenes is generally transmitted when food is harvested, processed, prepared, packed, transported or stored in environments contaminated with L. monocytogenes. Environments can be contaminated by raw materials, water, soil, and incoming air. Pets can also spread the bacteria in the home environment if they eat food contaminated with L. monocytogenes.

Symptoms

There are a range of symptoms for listeriosis. Depending on the severity of the illness, symptoms may last from days to several weeks. Mild symptoms may include a fever, muscle aches, nausea, vomiting, and diarrhea. If the more severe form of listeriosis develops, symptoms may include headache, stiff neck, confusion, loss of balance, and convulsions. For the very young, the elderly, and the immune-compromised listeriosis can result in death.

People infected with L. monocytogenes may start to see symptoms in a few hours or as long as two to three days after eating contaminated food. More severe forms of listeriosis may take anywhere from three days to three months to develop.

Due to the range in severity of illness, people should consult their health care provider if they suspect that they have developed symptoms that resemble a[n] L. monocytogenes infection.

At-Risk Groups

The severity of listeriosis varies and in some cases can be fatal, especially among the elderly, people with weakened immune systems or chronic diseases.

Listeriosis can be particularly dangerous for pregnant women and their newborn babies, leading to serious complications with their pregnancy, including miscarriage and stillbirth. Babies born with a listeriosis infection may develop severe health complications that require immediate medical attention, lead to lifelong health problems, or result in death. Women who suspect they have symptoms of listeriosis [muscles aches, nausea, stiffness in neck, headaches, etc.] should seek medical care immediately and tell their health provider what they ate. Learn more about People at Risk of Foodborne Illness.

Foods Linked to U.S. Outbreaks of Listeriosis

Past listeriosis outbreaks in the U.S. have been linked to raw, unpasteurized milks and cheeses, ice cream, raw or processed vegetables, raw or processed fruits, raw or undercooked poultry, sausages, hot dogs, deli meats, and raw or smoked fish and other seafood. L. monocytogenes has also been found in raw pet food.

Preventing Foodborne Illness at Home 

The longer ready-to-eat refrigerated foods contaminated with L. monocytogenes are stored in the refrigerator, the more opportunity this pathogen has to grow. To slow down or prevent the growth of L. monocytogenes, set the refrigerator to 40 degrees Fahrenheit [4 degrees Celsius], and the freezer to 0 degrees Fahrenheit [-18 degrees Celsius].

Consumers should also follow these simple steps:

• Wash the inside walls and shelves of the refrigerator, cutting boards and countertops, and utensils that may have contacted contaminated foods; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water; dry with a clean cloth or paper towel that has not been previously used. 
• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.
• Wash hands with warm water and soap for at least 20 seconds before and after handling food and following any cleaning and sanitation process.
• Pregnant women, the elderly and those with weakened immune systems should avoid certain foods, including unpasteurized or raw milk, cheeses made from unpasteurized milk, raw fish raw sprouts and some other raw foods, which carry a high risk for L. monocytogenes.
• People with pets should take special care to avoid cross-contamination when preparing their pet’s food. Be sure to pick up and thoroughly wash food dishes as soon as pets are done eating, and prevent children, the elderly, and any other people with weak immune systems from handling or being exposed to the food or pets that have eaten potentially contaminated food.
• Consumers can also submit a voluntarily report, a complaint, or adverse event [illness or serious allergic reaction] related to a food product.

Advice for Restaurants and Retailers

Retailers and/or other food service operators who have handled recalled or other potentially contaminated food in their facilities should:

• Contact their local health department and communicate to their customers regarding possible exposure to L. monocytogenes.
• To prevent the growth of L. monocytogenes, set the refrigerator to 40 degrees Fahrenheit [4 degrees Celsius], and set the freezer to 0 degrees Fahrenheit [-18 degrees Celsius].
• Wash the inside walls and shelves of the refrigerator, cutting boards and countertops, and utensils that may have contacted contaminated foods; then sanitize them with a solution of one tablespoon of chlorine bleach to one gallon of hot water; dry with a clean cloth or paper towel that has not been previously used.
• Wash and sanitize display cases and surfaces used to potentially store, serve, or prepare potentially contaminated foods.
• Wash hands with warm water and soap following the cleaning and sanitation process. 
• Conduct regular frequent cleaning and sanitizing of cutting boards and utensils used in processing to help minimize the likelihood of cross-contamination. 

Unlike most bacteria, L. monocytogenes can grow at refrigeration temperatures and freezing will not eliminate or reduce the pathogen. The FDA recommends that retailers implement time and temperature controls to reduce the opportunity for the growth of L. monocytogenes.  L. monocytogenes can also cross-contaminate other food that has been cut and served on the same cutting board or stored in the same area. Retailers should check with your state for specific guidance. More information can be found in the FDA Food Code 2017.

Additional Information

Who to Contact

To report a complaint or adverse event [illness or serious allergic reaction], you can

Visit www.fda.gov/fcic for additional consumer and industry assistance.

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Outbreak of Foodborne Illness

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A Microbial Biorealm page on the genus Listeria monocytogenes

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Bacillales; Listeriaceae; Listeria; L.monocytogenes

Species

Listeria monocytogenes

Description and significance

Listeria monocytogenes are a Gram-positive rod-shaped bacterium that form single short chains [1], and can be resistant to the effects of freezing, drying, and heat [2] surprisingly well for a non spore forming bacterium. Listeria are mainly found in the soil, though Listeria monocytogenes, a pathogen, may specifically be found in raw foods, such as unpasteurized fluid milk [5], raw vegetables, raw and cooked poultry [4]. It has the ability to grow at low temperatures; thus, allowing it to grow in refrigerated foods. Listeria monocytogenes was thought to be exclusively associated as infections in animals, but recently, this pathogenic species has also been isolated, in its dormant form, in the intestinal tract of small percentage of the human population [3]. Because Listeria monocytogenes is an agent of listeriosis, a serious disease where the overt form has a severe mortality greater than 25 percent [3], sequencing of the bacterium’s genome is of significant importance. Sequencing the genome of this organism allows for the measurement and study of traits such as new aspects regarding virulence and evolution using comparative genomics and DNA arrays [6]. 16S rRNA cataloging studies have also been conducted to demonstrate Listeria monocytogenes’ close relationship to different stains of listeriae, based on genome size, GC-content and other various characteristics [7], which also helped place the bacterium within the bacterial phylogeny constructed by Woese [3].

Genome structure

The genome of Listeria monocytogenes strain EGD-e is just one of several stains of the bacterium that have been sequenced. Strain EGC-e is 2,944,528 base pairs long with 2853 open reading frames and a GC content of 39% [NCBI]. Other strains sequenced include Listeria monocytogenes str.4b F2365, which is 2,905,310 base pairs long with a GC content of 38% [NCBI]. Currently the genomes of Listeria monocytogenes str. 1/2a F6854, and Listeria monocytogenes str. 4b H7858 are being sequenced [8]. Listeria monocytogenes has a single circular chromosome. The ability of Listeria to inhabit a wide range of environments is attributed to the presence of 331 genes encoding different transport proteins, comprising 11.6% of the total gene compliment of L. monocytogenes. Listeria also has an extensive regulatory range occupying much of the total genome [8].

Cell structure and metabolism

Listeria monocytogenes do not form spores or branch and are motile via peritrichous flagella at room temperature [20º-25º], but surprisingly cannot synthesize flagella at body temperature [37º] [13]. Because Listeria monocytogenes are intracellular pathogens, virulence is associated with the ability of bacteria to move into host cells by polymerization of host cell actin at one end of the bacterium, which helps them propel through cytoplasm. Flagellar motility is used more for spread of the bacteria outside the host environment [9, 13].

Ecology

Listeria monocytogenes has been found widely distributed throughout the environment, especially in the soil and fecal matter. Studies have shown that infected animals may contribute to Listeria monocytogenes ’s dispersal into the environment through animal fecal matter and feedstuff [10]. Listeria monocytogenes, as an intracellular pathogen, has been associated with severe food borne infections in humans and animals, though rarely through raw animal-derived food products [11]. Listeria monocytogenes have also been shown to survive in different habitats with extreme conditions including high salt concentrations, high pH, and high temperature [3]. Listeria monocytogenes can also form biofilms, which enables them as a community to attach to solid surfaces where they proliferate and become extremely difficult to remove [20].

Pathology

Most Listeria monocytogenes are pathogenic to both animals and humans to some degree; however, the bacterium has been reported to be carried in the intestinal tract of a small percentage of the human population without apparent symptoms [3]. As with many different pathogens, the virulence of this bacterium varies depending on the particular strain and with the susceptibility of the victim. Listeria monocytogenes has been associated with ingested raw and contaminated foods, such as raw and pasteurized dairy products [5], raw vegetables, raw meats and smoked fish [3]. Because of its ability to grow at low temperatures, Listeria monocytogenes can be found growing in refrigerated foods as well [3]. Listeria monocytogenes causes the disease listeriosis in humans, with common manifestations in septicemia [12], meningitis [13], encephalitis [13], corneal ulcer [14], pneumonia [15], and cervical infections in pregnant women, which may have resulted in spontaneous abortion or stillbirth [13]. Patient symptoms include influenza- like symptoms, and gastrointestinal symptoms of vomiting and diarrhea [3]. When Listeria monocytogenes invades the gastrointestinal epithelium and then enters the host’s monocytes, macrophages, or polymorphonuclear leukocytes, it becomes blood-borne and multiplies, both intracellularly and extracellularly. Intracellularly, it has access to the brain and transplacental migration to the fetus in pregnant women [16]. In animals infected with Listeria monocytogenes, such as mice, the bacteria first appear in macrophages and then spread to hepatocytes in the liver [17]. The bacteria stimulate a response that includes the production of gamma interferons, macrophage activating factors and a cytotoxic T cell response [17]. The pathogenesis of Listeria monocytogenes thrives on its ability to survive and multiply in phagocytic host cells. Virulence is thus associated with the ability of the bacterium to move within the cytoplasm of the host cells by polymerization of host cell actin [9]. Secreting the enzyme invasion allows Listeria monocytogenes to penetrate host cells of the epithelial lining. The immune system can usually eliminate the infection before it spreads by using T lymphocytes specifically for Listeria antigens [17]. However, systemic disease may develop with a compromised immune system. Another virulence factor is the bacterium’s ability to bind to epithelial cells by means of adherence to D-galactose receptors on the host cell [16].

Application to Biotechnology

Listeria monocytogenes does not produce any known useful compounds or enzymes

Current Research

Research continues to be conducted on the characterization and function of Listeria monocytogenes [1,9,19, 20] to better understand its pathological activity and its continued effect on food products and household environments [2,16,18, 21]. These characterizations include studies that examine enzymes that the bacterium uses [1], that further investigate the mechanism of motility and infection [9], that study different growth factors via heat-killed organisms [19], and explore relationships within biofilm communities [20]. The genomes of several Listeria monocytogenes strains are in the process of being sequenced and with this information available, a more complete understanding of the natural history of this pathogen will be obtained. This understanding will further facilitate rational and effective control strategies to reduce human and animal listeriosis cases [10, 21].

References

1. Theivagt, A.E., Friesen, J.A. [2006]. “Purification and characterization of Listeria monocytogenes HMG-CoA reductase” FASEB Journal 20 [4, Part 1]: A472 MAR 6 2006.

2. Sallami, Lamjed; Marcotte, Michele; Naim, Fadia; Ouattara, Blaise; Leblanc, Claude; Saucier, Linda [2006]. “Heat inactivation of Listeria monocytogenes and Salmonella enterica serovar Typhi in a typical bologna matrix during an industrial cooking-cooling cycle” Journal of Food Protection 69 [12]: 3025-3030 DEC 2006.

3. Rouquette, C., Berche, P. [1996]. The pathogenesis of infection by Listeria monocytogenes. 12[2]: 245-258.

4. Dykes, Gary A. [2003]. “Influence of the adaptation of Listeria monocytogenes populations to structured or homogeneous habitats on subsequent growth on chilled processed meat.” International Journal of Food Microbiology 85 [3] : 301-306 25 August, 2003.

5. Fleming, D.W., S.L. Cochi, K.L. McDonald, J.Brondum, P.S. Hayes, B.D. Plikaytis, M.B. Holmes, A. Audurier, C.V. Broome, and A.L. Reingold. [1985]. “Pasteurized milk as a vehicle of infection in an outbreak of listeriosis” N.Engl. J. Med. 312:404-407.

6. Doumith M, Cazalet C, Simoes N, Frangeul L, Jacquet C, Kunst F, Martin P, Cossart P, Glaser P, Buchrieser C. [2004] “New aspects regarding evolution and virulence of Listeria monocytogenes revealed by comparative genomics and DNA arrays.” Infect Immun. 2004 Feb;72[2]:1072-83.

7. Feresu SB, Jones D. [1988]. “Taxonomic studies on Brochothrix, Erysipelothrix, Listeria and atypical lactobacilli” J Gen Microbiol. 1988 May;134[5]:1165-83.

8. Hain, T. [2006]. Whole-genome sequence of Listeria welshimeri reveals common steps in genome reduction with Listeria innocua as compared to Listeria monocytogenes. Journal of bacteriology, 188[21], 7405-7415.

9. O'Neil, H. [2006]. Listeria monocytogenes flagella are used for motility, not as adhesins, to increase host cell invasion. Infection and immunity, 74[12], 6675-6681.

10. Nightingale, K.K., et al. [2004]. Ecology and Transmission of Listeria monocytogenes Infecting Ruminants and in the Farm Environment. American Society for Microbiology, 2004 Aug: 4458-4467.\

11. Mead, P.S., L. Slutsker, V. Dietz, L.F. McCraig, J.S. Bresee, C. Shapiro, P.M. Griffin, and R.V. Tauxe. [1999] Food-related illness and death in the United States. Emerg. Infect. Dis. 5:607-625.

12. Gray, M.L., and A.H. Killinger. [1966]. Listeria monocytogenes and listeric infection. Bacteriol. Rev. 30:309-382.

13. Dussurget, O., Pizarro-Cerda, J., Cossart, P. [2004]. Molecular determinants of Listeria monocytogenes virulence. Annuak Review of Microbiology 58: 587-610.

14. Holland, S., E. Alfonso, H. Gelender, D. Heidemann, A. Mendelsohn, S. Ullman, and D. Miller. [1987]. Corneal ulcer due to Listeria monocytogenes. Cornea 6:144-146.

15. Whitelock-Jones, L., J. Carswell, and K.C. Rassmussen. [1989]. Listera pneumonia. A case report. South African Medical Jounal 75:188-189.

16. Kazmierczak, M.J., Wiedmann, M., Boor, K.J. [2005]. Alternative Sigma Factors and Their Roles in Bacterial Virulence 69[4]: 527-543.

17. Mansfield, B.E., Freitag, N.E. [2003]. Listeria monocytogenes pathogenesis: Exploration of alternative hosts. Abstracts of the General Meeting of the American Society for Microbiology 103: B-186.

18. Wagner, M.; Auer, B.; Trittremmel, C., et al. [2007] Survey on the Listeria contamination of ready-to-eat food products and household environments in Vienna, Austria. Zoonoses Public Health 54 [1]: 16-22.

19. Sato, F., Imaizumi, T., Sashinami, H., et al. [2007]. Upregulation of vascular endothelial growth factor by heat-killed Listeria monocytogenes in macrophages. Biochemical and Biophysical Research Communications 354 [2]: 608-612.

20. Harvey, J., Keenan, K. P., Gilmour, A. [2007]. Assessing biofilm formation by Listeria monocytogenes strains. Food Microbiology [London] 24 [4]: 380-392.

21. Aarnisalo, K., Lunden, J., Korkeala, H., et al. [2007]. Susceptibility of Listeria monocytogenes strains to disinfectants and chlorinated alkaline cleaners at cold temperatures. LWT - Food Science and Technology 40 [6]: 1041-1048.

Edited by Jenny Hung student of Rachel Larsen and Kit Pogliano

KMG