Listeria monocytogenes

Listeria monocytogenes

Taxobox | name = "Listeria monocytogenes"



image_width = 240px
regnum = Bacteria
divisio = Firmicutes
classis = Bacilli
ordo = Bacillales
familia = Listeriaceae
genus = "Listeria"
species = "L. monocytogenes"
binomial = "Listeria monocytogenes"
binomial_authority = (Murray "et al." 1926)

"Listeria monocytogenes" is a Gram-positive bacterium, in the division Firmicutes, named for Joseph Lister. Motile via flagella at 30°C and below but usually not at 37°CGründling, A., Burrack, L.S., Bouwer, H.G.A., Higgins, D.E. 2004. Listeria monocytogenes regulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence. Proc. Natl. Acad. Sci. USA. 101:12316–12323..] , "L. monocytogenes" can instead move within eukaryotic cells by explosive polymerization of actin filaments (known as "comet tails" or "actin rockets").

Studies suggest that up to 10% of human gastrointestinal tracts may be colonized by "L. monocytogenes". [Ramaswamy, Vidhya and Cresence, Vincent Mary. "Listeria - Review of Epidemiology and Pathogenesis." J Microbiol Immunol Infect. (2007). 40:4-13]

Nevertheless, clinical diseases due to "L. monocytogenes" are more frequently recognized by veterinarians, especially as meningo-encephalitis in ruminants. See : listeriosis in animals.

Due to its frequent pathogenicity causing meningitis in newborns (acquired transvaginally), pregnant mothers are often advised not to eat soft cheeses such as Brie, Camembert, feta and queso blanco fresco, which may be contaminated with and permit growth of "L. monocytogenes" Genigeorgis, C.,Carniciu, M., Dutulescu, D., Farver, T.B. 1991. Growth and survival of Listeria monocytogenes in market cheeses stored at 4 to 30 degrees C. J. Food Prot. 54(9):662-668.] . It is the third most common cause of meningitis in newborns.

More recently, "L. monocytogenes" has been used as the model organism to illustrate the Patho-biotechnology concept.

History

"L. monocytogenes" was first described by E.G.D.Murray in 1926 based on six cases of sudden death in young rabbits. [ Murray, E.G.D., Webb, R.E., Swann, M.B.R. 1926. A disease of rabbits characterized by a large mononuclear leucocytosis, caused by a hitherto undescribed bacillus Bacterium monocytogenes (n. sp.). J. Pathol. Bacteriol. 29: 407– 439.] Murray referred to the organism as "Bacterium monocytogenes" before J.H. Harvey Pirie changed the genus name to Listeria in 1940. [Pirie, J.H.H. 1940. Listeria: change of name for a genus of bacteria. Nature. 145:264] . Although clinical descriptions of "L. monocyotogenes" infection in both animals and humans were published in the 1920s, not until 1952 in East Germany was it recognized as a significant cause of neonatal sepsis and meningitis. [Potel, J. 1952. Zur Granulomatosis infantiseptica. Zentr. Bakteriol. I. Orig. 158: 329-331] Listeriosis in adults would later be associated with patients living with compromised immune systems, such as individuals taking immunosuppressant drugs and corticosteroids for malignancies or organ transplants, and those with HIV infection. [Schlech, W.F. III. 2001. Foodborne listeriosis. Clin. Infect. Dis. 31: 770-775. ]

It wasn't until 1981 however that "L. monocytogenes" was identified as a cause of foodborne illness. An outbreak of listeriosis in Halifax, Nova Scotia involving 41 cases and 18 deaths, mostly in pregnant women and neonates, was epidemiologically linked to the consumption of coleslaw containing cabbage that had been treated with "L. monocytogenes" contaminated raw sheep manure. [Schlech, W.F., Lavigne, P.M., Bortolussi, R.A., Allen, A.C., Haldane, E.V., Wort, A.J., Hightower, A.W., Johnson, S.E., King, S.H., Nicholls, E.S. and Broome, C.V. 1983. Epidemic listeriosis—evidence for transmission by food. New Engl. J. Med. 308:203–206. ] Since then a number of cases of foodborne listeriosis have been reported, and "L. monocytogenes" is now widely recognized as an important hazard in the food industry. [Ryser, E.T., Marth, E.H. (Eds.) 1999. Listeria, Listeriosis, and Food. Safety, 2nd edn. Marcel Dekker, New York.]

Pathogenesis

Infection by "L. monocytogenes" causes the disease listeriosis. The manifestations of listeriosis include septicemiaGray, M. L., and A. H. Killinger. 1966. Listeria monocytogenes and listeric infection. Bacteriol. Rev. 30:309-382.] , meningitis (or meningoencephalitis), encephalitisArmstrong, R. W., and P. C. Fung. 1993. Brainstem encephalitis (Rhombencephalitis) due to Listeria monocytogenes: case report and review. Clin. Infect. Dis. 16:689-702.] , corneal ulcerHolland, S., E. Alfonso, . Gelender, D. Heidemann, A. Mendelsohn, S. Ullman, and D. Miller. 1987. Corneal ulcer due to Listeria monocytogenes. Cornea 6:144-146.] , pneumoniaWhitelock-Jones, L., J. Carswell, and K. C. Rassmussen. 1989. Listeria pneumonia. A case report. South African Medical Journal 75:188-189.] , and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion (2nd/3rd trimester) or stillbirth. Surviving neonates of Fetomaternal Listeriosis may suffer granulomatosis infantiseptica - pyogenic granulomas distributed over the whole body, and may suffer from physical retardation. Influenza-like symptoms, including persistent fever, usually precede the onset of the aforementioned disorders. Gastrointestinal symptoms such as nausea, vomiting, and diarrhea may precede more serious forms of listeriosis or may be the only symptoms expressed. Gastrointestinal symptoms were epidemiologically associated with use of antacids or cimetidine. The onset time to serious forms of listeriosis is unknown but may range from a few days to three weeks. The onset time to gastrointestinal symptoms is unknown but probably exceeds 12 hours. An early study suggeseted that "L. monocytogenes" was unique among Gram-positive bacteria in that it possessed lipopolysaccharideWexler, H., and J. D. Oppenheim. 1979. Isolation, characterization, and biological properties of an endotoxin-like material from the gram-positive organism Listeria monocytogenes. Infect. Immun. 23:845-857.] , which served as an endotoxin. A later study did not support these findings SHYAMAL K. MAITRA,RONALD NACHUM, AND FREDERICK C. PEARSON. 1986. Establishment of Beta-Hydroxy Fatty Acids as Chemical Marker Molecules for Bacterial Endotoxin by Gas Chromatography-Mass Spectrometry. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Sept. 1986, p. 510-514] .

The infective dose of "L. monocytogenes" varies with the strain and with the susceptibility of the victim. From cases contracted through raw or supposedly pasteurized milk, one may safely assume that in susceptible persons, fewer than 1,000 total organisms may cause disease. "L. monocytogenes" may invade the gastrointestinal epithelium. Once the bacterium enters the host's monocytes, macrophages, or polymorphonuclear leukocytes, it becomes blood-borne (septicemic) and can grow. Its presence intracellularly in phagocytic cells also permits access to the brain and probably transplacental migration to the fetus in pregnant women. The pathogenesis of "L. monocytogenes" centers on its ability to survive and multiply in phagocytic host cells.

Treatment

When listeric meningitis occurs, the overall mortality may reach 70%; from septicemia 50%, from perinatal/neonatal infections greater than 80%. In infections during pregnancy, the mother usually survives. Reports of successful treatment with parenteral penicillin or ampicillin exist. Trimethoprim-sulfamethoxazole has been shown effective in patients allergic to penicillin.

Bacteriophage treatments have been developed by several companies. EBI Food Safety and Intralytix both have products suitable for treatment of the bacteria. The FDA of the United States approved a cocktail of six bacteriophages from Intralytix, and a one type phage product from EBI Food Safety designed to kill the bacteria "L. monocytogenes". Uses would potentially include spraying it on fruits and ready-to-eat meat such as sliced ham and turkey.

Use as a transfection vector

Because "L. monocytogenes" is an intracellular parasite, some studies have used this bacteria as a vector to deliver genes "in vitro." Current transfection efficiency remains poor. One example of the successful use of "L. monocytogenes" in "in vitro" transfer technologies is in the delivery of gene therapies for cystic fibrosis cases.Fact|date=August 2008

Cancer vaccine

A live attenuated "L. monocytogenes" cancer vaccine named Lovaxin C is under development as a possible treatment for cervical carcinoma.cite journal|title=Live Listeria Vaccine Proves Safe Against End-Stage Cervical Ca in Human Trial|author=Fran Lowry|journal=Ob.Gyn. News Vol.43, No.10, page 2|date=05-15-2008]

Detection

The methods for analysis of food are complex and time-consuming. The present U.S. Food and Drug Administration (FDA) method, revised in September, 1990, requires 24 and 48 hours of enrichment, followed by a variety of other tests. Total time to identification takes from 5 to 7 days, but the announcement of specific nonradiolabled DNA probes should soon allow a simpler and faster confirmation of suspect isolates.

Recombinant DNA technology may even permit 2-to-3 day positive analysis in the future. Currently, the FDA is collaborating in adapting its methodology to quantitate very low numbers of the organisms in foods.

Bio-Rad Laboratories (www.bio-rad.com) have come up with media called Rapid'L.Mono Medium which cut short time to 48 hours

Epidemiology

Researchers have found "L. monocytogenes" in at least 37 mammalian species, both domesticated and feral, as well as in at least 17 species of birds and possibly in some species of fish and shellfish. Laboratories can isolate "L. monocytogenes" from soil, silage, and other environmental sources. "L. monocytogenes" is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most "L. monocytogenes" are pathogenic to some degree.

Routes of infection

"L. monocytogenes" has been associated with such foods as raw milk, pasteurized fluid milkFleming, D. W., S. L. Cochi, K. L. MacDonald, 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.] , cheeses (particularly soft-ripened varieties), ice cream, raw vegetables, fermented raw-meat sausages, raw and cooked poultry, raw meats (of all types), and raw and smoked fish. Its ability to grow at temperatures as low as 0°C permits multiplication in refrigerated foods. In refrigeration temperature such as 4°C the amount of ferric iron promotes the growth of "L. monocytogenes".Dykes, G. A., Dworaczek (Kubo), M. 2002. Influence of interactions between temperature, ferric ammonium citrate and glycine betaine on the growth of "Listeria monocytogenes" in a defined medium. Lett Appl Microbiol. 35(6):538-42.]

Infectious Cycle

The primary site of infection is the intestinal epithelium where the bacteria invade non-phagocytic cells via the "zipper" mechanism. Uptake is stimulated by the binding of listerial internalins (Inl) to host cell adhesion factors such as E-cadherin or Met. This binding activates certain Rho-GTPases which subsequently bind and stabilize Wiskott Aldrich Syndrome Protein (WASp). WASp can then bind the Arp2/3 complex and serve as an actin nucleation point. Subsequent actin polymerization extends the cell membrane around the bacterium, eventually engulfing it. The net effect of internalin binding is to exploit the junction forming-apparatus of the host into internalizing the bacterium. Note that "L. monocytogenes" can also invade phagocytic cells (e.g. macrophages) but only requires internalins for invasion of non-phagocytic cells.

Following internalisation, the bacterium must escape from the vacuole/phagosome before fusion with a lysosome can occur. Two main virulence factors which allow the bacterium to escape are listeriolysin O (LLO - encoded by "hly") and phospholipase C B ("plc"B). Secretion of LLO and PlcB disrupts the vacuolar membrane and allows the bacterium to escape into the cytoplasm where it may proliferate.

Once in the cytoplasm, "L. monocytogenes" exploits host actin for the second time. ActA proteins associated with the old bacterial cell pole (being a bacilli, "L. monocytogenes" septates in the middle of the cell and thus has one new pole and one old pole) are capable of binding the Arp2/3 complex and thus induce actin nucleation at a specific area of the bacterial cell surface. Actin polymerization then propels the bacterium unidirectionally into the host cell membrane. The protrusion which is formed may then be internalised by a neighbouring cell, forming a double-membrane vacuole from which the bacterium must escape using LLO and PlcB.

Outbreaks

An outbreak of "L. monocytogenes" occurred in Ontario Canada beginning in August of 2008. By the 28th of August, there were 29 confirmed cases of listeriosis wth 16 deaths.' [http://www.cbc.ca/canada/story/2008/08/28/listeria-thurs.html CBC news, 8 people now dead because of listeriosis: health official] ]

References

External links

* [http://vm.cfsan.fda.gov/~mow/chap6.html/ U.S. Food and Drug Administration. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Listeria monocytogenes]
* [http://www.phac-aspc.gc.ca/alert-alerte/listeria_200808-eng.php Public Health Agency of Canada]


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