|
''Yersinia enterocolitica'' is a Gram-negative bacillus-shaped bacterium, belonging to the family Enterobacteriaceae. ''Y. enterocolitica'' infection causes the disease yersiniosis, which is a zoonotic disease occurring in humans, as well as a wide array of animals such as cattle, deer, pigs, and birds. Many of these animals recover from the disease and become asymptomatic carriers. It infects the host by sticking to the cells of the host using trimeric autotransporter adhesins (TAAs). The genus ''Yersinia'' includes 11 species: ''Y. pestis, Y. pseudotuberculosis, Y. enterocolitica, Y. frederiksenii,'' ''Y. intermedia, Y. kristensenii, Y. bercovieri,'' ''Y. mollaretii, Y. rohdei, Y. aldovae'' and ''Y. ruckeri''. Among them, only ''Y. pestis, Y. pseudotuberculosis'', and certain strains of ''Y. enterocolitica'' are of pathogenic importance for humans and certain warm-blooded animals, whereas the other species are of environmental origin and may, at best, act as opportunists. However, ''Yersinia'' strains can be isolated from clinical materials, so have to be identified at the species level. ''Y. enterocolitica'' is a heterogeneous group of strains, which are traditionally classified by biotyping into six biogroups on the basis of phenotypic characteristics, and by serotyping into more than 57 O serogroups, on the basis of their O (lipopolysaccharide or LPS) surface antigen. Five of the six biogroups (1B and 2–5) are regarded as pathogens. However, only a few of these serogroups have been associated with disease in either humans or animals. Strains that belong to serogroups O:3 (biogroup 4), O:5,27 (biogroups 2 and 3), O:8 (biogroup 1B), and O:9 (biogroup 2) are most frequently isolated worldwide from human samples. However, the most important ''Y. enterocolitica'' serogroup in many European countries is serogroup O:3 followed by O:9, whereas the serogroup O:8 is mainly detected in the United States. ''Y. enterocolitica'' is widespread in nature, occurring in reservoirs ranging from the intestinal tracts of numerous mammals, avian species, cold-blooded species, and even from terrestrial and aquatic niches. Most environmental isolates are avirulent; however, isolates recovered from porcine sources contain human pathogenic serogroups. In addition, dogs, sheep, wild rodents, and environmental water may also be a reservoir of pathogenic ''Y. enterocolitica ''strains. Human pathogenic strains are usually confined to the intestinal tract and lead to enteritis/diarrhea. ==Signs and symptoms== The portal of entry is the gastrointestinal tract. The organism is acquired usually by insufficiently cooked pork or contaminated water, meat, or milk. Acute ''Y. enterocolitica'' infections usually lead to mild self-limiting enterocolitis or terminal ileitis and adenitis in humans. Symptoms may include watery or bloody diarrhea and fever, resembling appendicitis or salmonellosis or shigellosis. After oral uptake, ''Yersinia'' species replicate in the terminal ileum and invade Peyer's patches. From here they can disseminate further to mesenteric lymph nodes causing lymphadenopathy. This condition can be confused with appendicitis, so is called pseudoappendicitis. In immunosuppressed individuals, they can disseminate from the gut to liver and spleen and form abscesses. Because ''Yersinia'' species are siderophilic (iron-loving) bacteria, people with hereditary hemochromatosis (a disease resulting in high body iron levels) are more susceptible to infection with ''Yersinia'' (and other siderophilic bacteria). In fact, the most common contaminant of stored blood is ''Y. enterocolitica''.〔Goljan, Edward F. Rapid Review Pathology. Second Edition. Page 279, Table 15-1.〕 See yersiniosis for further 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「Yersinia enterocolitica」の詳細全文を読む スポンサード リンク
|