stx1

Stx1, short for Shiga toxin 1, is one of the major Shiga toxins produced by certain bacterial pathogens, notably Shigella dysenteriae type 1 and many shiga toxin–producing Escherichia coli (STEC). Like Shiga toxin 2 (Stx2), Stx1 is a potent AB5 ribosome-inactivating toxin that can cause severe gastrointestinal and systemic illness. The two toxins can occur separately or together in STEC infections, and Stx2 is often associated with a higher risk of hemolytic uremic syndrome (HUS).

The toxin is structured as an A subunit linked to a pentamer of B subunits. The B subunits bind to the globotriaosylceramide (Gb3) receptor on mammalian cells, enabling entry. The A subunit is an enzyme that depurinates a specific adenine residue on the 28S rRNA of the 60S ribosomal subunit, halting protein synthesis and triggering cell death. Cells with Gb3 receptors, including renal endothelial cells, are particularly affected, contributing to the toxin’s severe systemic manifestations.

Genetically, stx1 genes are carried by bacteriophages that infect Shigella and certain STEC strains. There are documented subtypes of Stx1, including Stx1a, Stx1c, and Stx1d, which differ slightly in sequence and potency. Expression is linked to phage induction and the bacterial host’s SOS response.

Clinically, Stx1 exposure typically presents with acute diarrhea that can be bloody, and in severe cases may progress to HUS, especially in children. Treatment is supportive; antibiotics can provoke phage induction and toxin release, so they are generally avoided. Prevention emphasizes food safety, proper cooking, pasteurization, and avoidance of contaminated water. Diagnosis relies on stool testing for Shiga toxins and related virulence factors.