What is the Shigella infection?

Updated: Apr 03, 2018
  • Author: Jaya Sureshbabu, MBBS, MRCPCH(UK), MRCPI(Paeds), MRCPS(Glasg), DCH(Glasg); Chief Editor: Russell W Steele, MD  more...
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Answer

Shigella organisms are a group of gram-negative, facultative intracellular pathogens. They were recognized as the etiologic agents of bacillary dysentery or shigellosis in the 1890s. Shigella were discovered over 100 years ago by a Japanese microbiologist named Shiga, for whom the genus is named. Shigella was adopted as a genus in the 1950s. These organisms are members of the family Enterobacteriaceae and tribe Escherichieae; they are grouped into 4 species: Shigelladysenteriae, Shigellaflexneri, Shigellaboydii, and Shigellasonnei, also known as groups A, B, C, and D, respectively. [1]  They are nonmotile, non – spore forming, rod shaped, and nonencapsulated. Subgroups and serotypes are differentiated from each other by their biochemical characteristics (e.g., ability to ferment D-mannitol) and antigenic properties. Group A has 15 serotypes, group B has 8 serotypes, group C has 19 serotypes, and group D has 1 serotype.

This illustration depicts a three-dimensional (3D) This illustration depicts a three-dimensional (3D), computer-generated image of a number of rod-shaped, drug-resistant, Shigella sp. bacteria. The artistic recreation was based upon scanning electron microscopic (SEM) imagery. Note that the exterior of the Shigella bacteria is fimbriated, covered by numerous thin, hair-like projections, imparting a furry appearance. Courtesy of the Centers for Disease Control (CDC)/James Archer.

Geographic distribution and antimicrobial susceptibility varies with different species. S dysenteriae serotype 1 causes deadly epidemics, S boydii is restricted to the Indian subcontinent, and S flexneri and S sonnei are prevalent in developing and developed countries, respectively. S flexneri, enteroinvasive gram-negative bacteria, is responsible for the worldwide endemic form of bacillary dysentery.


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