Rank: Species
Lineage: Bacteria;Proteobacteria;Gammaproteobacteria;Enterobacterales;Enterobacteriaceae;Shigella;Shigella dysenteriae
Description: Shigella. This genus is named for the Japanese scientist (Shiga) who first discovered these organisms in the 1890s. They are closely related to the Escherichia group, and may be considered the same species. These organisms are human-specific pathogens that are transmitted via contaminated food and water and are the leading causes of endemic bacillary dysentery, causing over 160 million cases of infection and 1 million deaths yearly worldwide. The bacteria infect the epithelial lining of the colon, causing acute inflammation by entering the host cell cytoplasm and spreading intercellularly. Shigella spp. are extremely virulent organisms that can cause an active infection after a very low exposure. Virulence functions are contained on pathogenicity islands (PAIs) that are scattered around the chromosome or on large virulence plasmids. Both the type III secretion system, which delivers effector molecules into the host cell, and some of the translocated effectors such as the invasion plasmid antigens (Ipas), are encoded on the plasmid. Two important cytotoxins (shigatoxins Stx1 and 2) are carried by phage that have integrated into the chromosome, one of which inhibits protein synthesis once it enters the eukaryotic cell. One important aspect of Shigella pathogenesis is the intercellular spreading phenotype. The bacterium produces a surface protein that localizes to one pole of the cell (IcsA) which binds to and promotes actin polymerization, resulting in movement of the bacterium through the cell cytoplasm, and eventually to neighboring cells, which results in inflammatory destruction of the mucosal lining. Shigella dysenteriae. This species is the major cause of Shigella-related deaths in developing nations, mostly in young children.
Reference Material:
https://www.ncbi.nlm.nih.gov/genome/?term=Shigella%20dysenteriae
