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''Listeria monocytogenes'' is the bacterium that causes the infection listeriosis. It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the host's cells and is one of the most virulent foodborne pathogens, with 20 to 30% of clinical infections resulting in death. Responsible for an estimated 1,600 illnesses and 260 deaths in the United States (U.S.) annually, listeriosis is the third-leading cause of death among foodborne bacterial pathogens, with fatality rates exceeding even ''Salmonella'' and ''Clostridium botulinum''. ''L. monocytogenes'' is a Gram-positive bacterium, in the division Firmicutes, named after Joseph Lister. Motile via flagella at 30°C and below, but usually not at 37°C, ''L. monocytogenes'' can instead move within eukaryotic cells by explosive polymerization of actin filaments (known as comet tails or actin rockets). Studies suggest up to 10% of human gastrointestinal tracts may be colonized by ''L. monocytogenes''.〔 Nevertheless, clinical diseases due to ''L. monocytogenes'' are more frequently recognized by veterinarians, especially as meningoencephalitis 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''. It is the third-most-common cause of meningitis in newborns. ''L. monocytogenes'' can infect the brain, spinal cord membranes and/or the bloodstream of the host through the ingestion of contaminated food such as unpasteurized dairy or raw foods. == Classification == ''L. monocytogenes'' is a Gram-positive, nonspore-forming, motile, facultatively anaerobic, rod-shaped bacterium. It is catalase-positive and oxidase-negative, and expresses a beta hemolysin, which causes destruction of red blood cells. This bacterium exhibits characteristic tumbling motility when viewed with light microscopy. Although ''L. monocytogenes'' is actively motile by means of peritrichous flagella at room temperature (20−25°C), the organism does not synthesize flagella at body temperatures (37°C).〔Todar, K. (2008). ("Listeria monocytogenes" ). Todar's Online Textbook of Bacteriology. Retrieved January 28, 2009.〕 The genus ''Listeria'' belongs to the class Bacilli and the order Bacillales, which also includes ''Bacillus'' and ''Staphylococcus''. 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.'' ''L. 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〕 Both ''L. ivanovii'' and ''L. monocytogenes'' are pathogenic in mice, but only ''L. monocytogenes'' is consistently associated with human illness.〔Seafood HACCP Alliance (2007). ("Compendium of Fish and Fishery Product Processes, Hazards, and Controls, Chapter 15: ''Listeria monocytogenes''". ) Seafood Network Information Center. Retrieved January 28, 2009.〕 The 13 serotypes of ''L. monocytogenes'' can cause disease, but more than 90% of human isolates belong to only three serotypes: 1/2a, 1/2b, and 4b. ''L. monocytogenes'' serotype 4b strains are responsible for 33 to 5% of sporadic human cases worldwide and for all major foodborne outbreaks in Europe and North America since the 1980s. 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 monocytogenes」の詳細全文を読む スポンサード リンク
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