Shigella
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221966375
2008-06-26T22:17:28Z
216.203.80.125
/* Pathogenesis */
{{Taxobox
| color = lightgrey
| name = '''''Shigella'''''| image= Shigella_stool.jpg
| image_caption=[[micrograph|Photomicrograph]] of ''Shigella'' sp. in a stool specimen
| regnum = [[Bacterium|Bacteria]]
| phylum = [[Proteobacteria]]
| classis = [[Gamma Proteobacteria]]
| ordo = [[Enterobacteriaceae|Enterobacteriales]]
| familia = [[Enterobacteriaceae]]
| genus = '''''Shigella'''''
| genus_authority = Castellani & Chalmers 1919
| subdivision_ranks = Species
| subdivision =
''[[Shigella boydii|S. boydii]]''<br />
''[[Shigella dysenteriae|S. dysenteriae]]''<br />
''[[Shigella flexneri|S. flexneri]]''<br />
''[[Shigella sonnei|S. sonnei]]''<br />
}}
: ''This article is about the bacteria. For the disease, see [[shigellosis]]''
'''''Shigella''''' is a [[genus]] of [[Gram-negative]], [[Endospore|non-spore forming]] rod-shaped [[bacterium|bacteria]] closely related to ''[[Escherichia coli]]'' and ''[[Salmonella]]''. The causative agent of human [[shigellosis]], ''Shigella'' also cause disease in other [[primate]]s, but not in other mammals.<ref>{{cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 |isbn = 0-8385-8529-9 }}</ref>
== Classification ==
''Shigella'' species are classified by four [[serogroup]]s:
* Serogroup ''A'': ''[[Shigella dysenteriae|S. dysenteriae]]'' (12 [[serovar|serotype]]s)
* Serogroup ''B'': ''[[Shigella flexneri|S. flexneri]]'' (6 serotypes)
* Serogroup ''C'': ''[[Shigella boydii|S. boydii]]'' (23 serotypes)
* Serogroup ''D'': ''[[Shigella sonnei|S. sonnei]]'' (1 serotype)
Group ''A''–''C'' are physiologically similar; ''S. sonnei'' (group ''D'') can be differentiated on the basis of biochemical metabolism assays.<ref>{{cite book | author = Hale TL, Keusch GT | title = ''''''Shigella'''''': Structure, Classification, and Antigenic Types. ''in:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1269 | isbn = 0-9631172-1-1 }}</ref>
== Pathogenesis ==
''Shigella'' infection is typically via ingestion (fecal–oral contamination); depending on age and condition of the host as few as ten bacterial cells can be enough to cause an infection. ''Shigella'' cause [[dysentery]] that results in the destruction of the epithelial cells of the intestinal mucosa in the [[cecum]] and [[rectum]]. Some strains produce [[enterotoxin]] and [[Shiga toxin]], similar to the [[verotoxin]] of [[Escherichia coli O157 H7|''E. coli'' O157:H7]].<ref>{{cite book | author = Hale TL, Keusch GT | title = Shigella. ''in:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.chapter.1257 | isbn = 0-9631172-1-1 }}</ref> Both Shiga toxin and verotoxin are associated with causing [[hemolytic uremic syndrome]].
''Shigella'' invade the host through [[epithelial cell]]s of the [[large intestine]]. Using a [[Type III secretion system]] acting as a biological syringe, the bacterium injects ''IpaD'' protein into cell, triggering bacterial invasion and the subsequent [[lysis]] of [[Vacuole|vacuolar]] membranes using ''IpaB'' and ''IpaC'' proteins. It utilizes a mechanism for its motility by which its ''IcsA'' protein triggers actin polymerization in the host cell (via [[Wiskott-Aldrich syndrome protein|N-WASP]] recruitment of [[Arp2/3|Arp2/3 complexes]]) in a "rocket" propulsion fashion for cell-to-cell spread.
The most common symptoms are [[diarrhea]], [[fever]], [[nausea]], [[vomiting]], stomach cramps, and straining to have a bowel movement. The stool may contain blood, mucus, or pus (e.g. dysentery). In rare cases, young children may have [[seizure]]s. Symptoms can take as long as a week to show up, but most often begin two to four days after ingestion. Symptoms usually last for several days, but can last for weeks. Shigella is implicated as one of the pathogenic causes of [[reactive arthritis]] worldwide.<ref>{{cite journal |author=Hill Gaston JS, Lillicrap MS |title=Arthritis associated with enteric infection |journal=Best practice & research. Clinical rheumatology |volume=17 |issue=2 |pages=219–39 |year=2003 |pmid=12787523|doi=10.1016/S1521-6942(02)00104-3}}</ref>
Severe dysentery can be treated with [[ampicillin]], [[Trimethoprim-sulfamethoxazole|TMP-SMX]], or [[fluoroquinolone]]s such as [[ciprofloxacin]] and of course rehydration.
Each of the ''Shigella'' genomes includes a virulence [[plasmid]] that encodes conserved primary virulence determinants. The ''Shigella'' [[chromosome]]s share most of their genes with that of ''E. coli'' K12 strain MG1655<ref name="Yang2005">{{cite journal |author=Yang F ''et al.'' |title=Genome dynamics and diversity of ''Shigella'' species, the etiologic agents of bacillary dysentery |journal=Nucleic Acids Res |volume=33 |issue=19 |pages=6445–58 |year=2005 |pmid=16275786 |doi=10.1093/nar/gki954}}</ref>
==External links==
* Genome information is available at the [http://www.ericbrc.org NIAID Enteropathogen Resource Integration Center (ERIC)]
== References ==
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== See also ==
[[TSI slant]], a selective test for enteric bacteria such as Shigella and Salmonella
[[Category:Enterobacteria]]
[[Category:Water-borne diseases]]
[[Category:Biological weapons]]
[[Category:Microbiology]]
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