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''Listeria'' is a genus of bacteria that contains 10 species,〔Jones, D. 1992. Current classification of the genus Listeria. In: Listeria 1992. Abstracts of ISOPOL XI, Copenhagen, Denmark). p. 7-8. ocourt, J., P. Boerlin, F.Grimont, C. Jacquet, and J-C. Piffaretti. 1992. Assignment of Listeria grayi and Listeria murrayi to a single species, Listeria grayi, with a revised description of Listeria grayi. Int. J. Syst. Bacteriol. 42:171-174.〕〔Boerlin et al. 1992. L. ivanovii subsp. londoniensis subsp. novi. Int. J. Syst. Bacteriol. 42:69-73. Jones, D., and H.P.R. Seeliger. 1986. International committee on systematic bacteriology. Subcommittee the taxonomy of Listeria. Int. J. Syst. Bacteriol. 36:117-118.〕 each containing two subspecies. Named after the British pioneer of sterile surgery Joseph Lister, the genus received its current name in 1940. ''Listeria'' species are gram-positive, rod-shaped, facultatively anaerobic, and non spore-forming. The major human pathogen in the ''Listeria'' genus is ''L. monocytogenes''. It is usually the causative agent of the relatively rare bacterial disease listeriosis, a serious infection caused by eating food contaminated with the bacteria. The disease affects pregnant women, newborns, adults with weakened immune systems, and the elderly. Listeriosis is a serious disease for humans; the overt form of the disease has a case-fatality rate of about 20%. The two main clinical manifestations are sepsis and meningitis. Meningitis is often complicated by encephalitis, when it is known as meningoencephalitis, a pathology that is unusual for bacterial infections. ''L. ivanovii'' is a pathogen of mammals, specifically ruminants, and has rarely caused listeriosis in humans.〔Christelle Guillet, Olivier Join-Lambert, Alban Le Monnier, Alexandre Leclercq, Frédéric Mechaï, Marie-France Mamzer-Bruneel, Magdalena K. Bielecka, Mariela Scortti, Olivier Disson, Patrick Berche, José Vazquez-Boland, Olivier Lortholary, and Marc Lecuit. Human Listeriosis Caused by Listeria ivanovii. ''Emerg Infect Dis.'' 2010 January; 16(1): 136–138.〕 ==Background== The first documented case of ''Listeria'' was in 1924. In the late 1920s, two researchers independently identified ''L. monocytogenes'' from animal outbreaks. They proposed the genus ''Listerella'' in honor of surgeon and early antiseptic advocate Joseph Lister , but that name was already in use for a slime mold and a protozoan. Eventually, the genus ''Listeria'' was proposed and accepted. All species within the ''Listeria'' genus are gram-positive, not spore-forming, catalase-positive rods. The genus ''Listeria'' was classified in the family Corynebacteriaceae through the seventh edition of ''Bergey's Manual of Systematic Bacteriology''. The 16S rRNA cataloging studies of Stackebrandt, et al. demonstrated that ''L. monocytogenes'' is a distinct taxon within the ''Lactobacillus-Bacillus'' branch of the bacterial phylogeny constructed by Wöse. In 2004, the genus was placed in the newly created family Listeriaceae. The only other genus in the family is ''Brochothrix''.〔Elliot T. Ryser, Elmer H. Marth. ''Listeria, Listeriosis, and Food Safety''. Second edition. Elmer Marth. 1999.〕 The genus ''Listeria'' currently contains 10 species: ''L. fleischmannii, L. grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. rocourtiae, L. seeligeri, L. weihenstephanensis '' and ''L. welshimeri.'' ''Listeria dinitrificans'', previously thought to be part of the ''Listeria'' genus, was reclassified into the new genus ''Jonesia''.〔M. D. Collins, S. Wallbanks, D. J. Lane, J. Shah, R. Nietupskin, J. Smida, M. Dorsch and E. Stackebrandt. Phylogenetic Analysis of the Genus ''Listeria'' Based on Reverse Transcriptase Sequencing of 16S rRNA. International Journal of Systematic and Evolutionary Microbiology. April 1991 vol. 41 no. 2 240–246〕 Under the microscope, ''Listeria'' species appear as small, gram-positive rods, which are sometimes arranged in short chains. In direct smears, they may be coccoid, so they can be mistaken for streptococci. Longer cells may resemble corynebacteria. Flagella are produced at room temperature, but not at 37°C. Hemolytic activity on blood agar has been used as a marker to distinguish ''L. monocytogenes'' from other ''Listeria'' species, but it is not an absolutely definitive criterion. Further biochemical characterization may be necessary to distinguish between the different species of ''Listeria''. ''Listeria'' can be found in soil, which can lead to vegetable contamination. Animals can also be carriers. ''Listeria'' has been found in uncooked meats, uncooked vegetables, fruit such as cantaloupes and apples, pasteurized or unpasteurized milk, foods made from milk, and processed foods. Pasteurization and sufficient cooking kill ''Listeria''; however, contamination may occur after cooking and before packaging. For example, meat-processing plants producing ready-to-eat foods, such as hot dogs and deli meats, must follow extensive sanitation policies and procedures to prevent ''Listeria'' contamination. ''Listeria monocytogenes'' is commonly found in soil, stream water, sewage, plants, and food. ''Listeria'' is responsible for listeriosis, a rare but potentially lethal foodborne illness. The case fatality rate for those with a severe form of infection may approach 25%. (''Salmonellosis'', in comparison, has a mortality rate estimated at less than 1%.) Although ''Listeria monocytogenes'' has low infectivity, it is hardy and can grow in temperatures from 4°C (39.2°F) (the temperature of a refrigerator), to 37°C (98.6°F), (the body's internal temperature).〔 Listeriosis is a serious illness, and the disease may manifest as meningitis, or affect newborns due to its ability to penetrate the endothelial layer of the placenta.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Listeria」の詳細全文を読む スポンサード リンク
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