Shiga toxin

Shiga toxin is a type of toxin produced by some strains of the bacterium Escherichia coli (E. coli) and Shigella. Named after Kiyoshi Shiga, who first discovered it in 1898, Shiga toxin is one of the primary causes of hemolytic uremic syndrome (HUS), a condition characterized by hemolytic anemia, acute kidney failure, and low platelet count.

Structure and Function

Shiga toxin is a two-part protein complex that includes one A subunit and five identical B subunits. The B subunits bind to a specific type of glycolipid on the surface of the host's cells, specifically Gb3. After binding, the A subunit is transported into the cell where it inhibits protein synthesis by cleaving a specific adenine base from the 28S rRNA of the 60S subunit of the ribosome. This action halts protein synthesis within the host cell and leads to cell death.

Pathogenesis

Shiga toxin is a key factor in the virulence of enterohemorrhagic and enteroinvasive E. coli and Shigella species. These bacteria can cause diseases such as dysentery and hemorrhagic colitis, which can progress to potentially fatal conditions like HUS. The toxin can also cause changes in the cytoskeleton of endothelial cells, which can lead to cell death and contribute to the development of HUS.

Treatment and Prevention

There is currently no specific treatment for diseases caused by Shiga toxin. Management of these conditions typically involves supportive care, including hydration and dialysis if necessary. Antibiotics are not typically used as they can induce the bacteria to release more toxin.

Prevention strategies include proper food handling and preparation techniques to avoid contamination with bacteria that produce Shiga toxin. Vaccines are also being researched and developed.

See Also

• Escherichia coli
• Shigella
• Hemolytic uremic syndrome
• Dysentery
• Hemorrhagic colitis

Shiga toxin Resources
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