stx2

Shiga toxin 2 (Stx2) is one of the Shiga toxins produced by Shiga toxin–producing Escherichia coli (STEC). The stx2 gene is carried by lambdoid prophages integrated into the bacterial chromosome and exists in several variants, including stx2a, stx2b, stx2c, and stx2d. Toxins are produced when the lysogenic phage enters a lytic cycle, and they can contribute to disease during STEC infections.

Stx2 is an AB5 ribosome-inactivating toxin. The A subunit is an N-glycosidase that cleaves a specific adenine from the 28S rRNA, halting protein synthesis. The B subunits form a pentamer that binds to the Gb3 receptor on host cell surfaces, with the renal microvascular endothelium particularly susceptible. This leads to cell injury, hemorrhagic colitis, and, in a subset of patients, hemolytic uremic syndrome (HUS), a potentially life-threatening microangiopathy.

Clinical significance: Infections with Stx2-producing STEC strains are associated with a higher risk of HUS compared with some Stx1-producing strains, with certain subtypes such as Stx2a and Stx2d linked to more severe outcomes. Outbreaks have been associated with contaminated beef, produce, and water. Children are at the greatest risk for severe complications.

Detection and treatment: Diagnosis relies on detection of the toxin or its encoding genes by immunoassays and PCR, often alongside culture and serotyping. Management is primarily supportive. Antibiotic use in suspected STEC infections is controversial and may increase toxin release, so it is generally avoided.

Prevention centers on food safety, proper hand hygiene, and prompt outbreak reporting.