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''Shigella'' () is a genus of Gram-negative, facultative anaerobic, non-spore-forming, non-motile, rod-shaped bacteria closely related to ''Salmonella''. The genus is named after Kiyoshi Shiga, who first discovered it in 1897. The causative agent of human shigellosis, ''Shigella'' causes disease in primates, but not in other mammals. It is only naturally found in humans and gorillas.〔(【引用サイトリンク】url=http://www.eazwv.org/sites/default/files/Files/Infectious%20Diseases%20Handbook/Fact%20Sheets/094%20Shigellosis.pdf )〕 During infection, it typically causes dysentery. ''Shigella'' is one of the leading bacterial causes of diarrhea worldwide. , the WHO reported that ''Shigella'' causes about 165 million cases of severe dysentery, with a million resulting in death each year, mostly among children in the developing world. == Classification == ''Shigella'' species are classified by four serogroups: * Serogroup ''A'': ''S. dysenteriae'' (15 serotypes) * Serogroup ''B'': ''S. flexneri'' (six serotypes) * Serogroup ''C'': ''S. boydii'' (19 serotypes) * Serogroup ''D'': ''S. sonnei'' (one serotype) Groups ''A''–''C'' are physiologically similar; ''S. sonnei'' (group ''D'') can be differentiated on the basis of biochemical metabolism assays. Three ''Shigella'' groups are the major disease-causing species: ''S. flexneri'' is the most frequently isolated species worldwide, and accounts for 60% of cases in the developing world; ''S. sonnei'' causes 77% of cases in the developed world, compared to only 15% of cases in the developing world; and ''S. dysenteriae'' is usually the cause of epidemics of dysentery, particularly in confined populations such as refugee camps.〔 Each of the ''Shigella'' genomes includes a virulence plasmid that encodes conserved primary virulence determinants. The ''Shigella'' chromosomes share most of their genes with those of ''E. coli'' K12 strain MG1655. Phylogenetic studies indicate ''Shigella'' is more appropriately treated as subgenus of ''Escherichia'', and that certain strains generally considered ''E. coli'' – such as ''E. coli'' O157:H7 – are better placed in ''Shigella'' (see ''Escherichia coli#Diversity'' for details). 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「Shigella」の詳細全文を読む スポンサード リンク
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