shigatoksiini

Shigatoksiini, known in English as Shiga toxin (Stx), is a potent cytotoxin produced by Shigella dysenteriae type 1 and by Shiga toxin–producing Escherichia coli (STEC), including strains such as Escherichia coli O157:H7. The toxin is a key virulence factor in severe gastrointestinal illness and its systemic complications.

Shiga toxin is an AB5 holotoxin composed of a single enzymatic A subunit and a pentamer of B subunits. The B subunits bind to the Gb3 receptors on host cells, allowing entry of the A subunit. Once inside, the A subunit acts as a ribosome-inactivating enzyme, removing an adenine from the 28S ribosomal RNA, which halts protein synthesis and can lead to cell death and inflammation.

Clinically, Shiga toxin–producing infections cause gastroenteritis that often presents with abdominal cramps and diarrhea, which may be bloody. Most cases are self-limiting, but STEC infections can progress to hemolytic-uremic syndrome (HUS), a serious condition characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, especially in children and the elderly. Shigella dysenteriae type 1 infections can cause severe dysentery with systemic illness.

Diagnosis relies on stool testing for Shiga toxin or detection of stx genes by molecular methods, along with culture. Treatment is mainly supportive; antibiotics are generally avoided in STEC infections because they may increase the risk of HUS. Prevention focuses on good hygiene, proper food handling and cooking, pasteurization, and avoidance of contaminated water.