Shiga toxin


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Shiga toxin

the endotoxin formed by Shigella dysenteriae type 1.

Shi·ga tox·in

(shē'gah tok'sin)
The endotoxin formed by Shigella dysenteriae type 1.

Shiga toxin

An extremely poisonous compound secreted by enteric bacteria that causes hemorrhagic and necrotic colitis. The toxin was formerly called verotoxin because of its effect on Vero cells.

Etiology

The toxin acts on the endothelial cells lining the blood vessels. The B subunits of the toxin bind to a component of the cell membrane known as Gb3 and enter the cell. When the protein is inside the cell, the A subunit interacts with the ribosomes to stop protein synthesis. Like the ricin toxin, the A subunit of Shiga toxin is an N-glycosidase that modifies the RNA component of the ribosome to stop protein synthesis, leading to the death of the cell. The breakdown of the endothelial cell lining leads to hemorrhage.

Symptoms

The first sign of shiga toxin activity is usually bloody diarrhea. This is because Shiga toxin is usually taken in with contaminated food or water.

See also: Shiga, Kiyoshi
References in periodicals archive ?
Proposed mode of action of Shiga toxin. Shiga toxin binds to the host cell receptor Gb3 (globotriaosylceramide, [P.sup.k] blood group antigen).
Presence of activatable Shiga toxin genotype (stx2d) in Shiga toxigenic Escherichia coli from livestock sources.
Second, laboratories that detect shiga toxin by antigen or molecular methods should also perform culture on sorbitol-MacConkey or MacConkey agar to recover the strain(s) for typing, which has major public health significance and may be clinically useful as well in some cases.
When found to have shiga toxins, the specimens would be sent to a reference laboratory abroad through the World Health Organisation (WHO).
DeMaria said the main concern is that treating diarrhea caused by the Shiga toxin strain with antibiotics could be a factor in precipitating the kidney disease, so antibiotics should be avoided, if possible.
As is generally recognized, mitochondrial cytochrome-c release is followed by the formation of cytochrome-c and dATP-dependent apoptotic protease activating factor (Apaf1)/caspase-9 complex, and, eventually, activation of caspase -3 (Tafani et al., 2000) The real molecular mechanisms are not known, however, in future study on the relationship between collagen and Shiga toxin apoptotic cell death could lead to a better understanding of this problem.
Moreover, intact bacteria carrying the gene don't secrete Shiga toxin into people.
coli: Shiga Toxin Methods and Protocols Dana Philpott, Frank Ebel Totowa, NJ: The Humana Press, 2002, 375 pp.
Bacterial infections are defined as isolation of the bacterium from a clinical specimen or detection of pathogen antigen, nucleic acid sequences, or, for STEC, ([dagger]) Shiga toxin or Shiga toxin genes.
Shiga toxin (Stx)-producing Escherichia coli (STEC) with the serotype O157:H7 is characterized by the possession of stx gene(s), the locus of enterocyte effacement (LEE)--encoded type 3 secretion system (T3SS), and a large virulence plasmid (pO157) that encodes enterohemolysin and other virulence factors, such as catalase-peroxidase KatP, a type II secretion system, and the protease EspP (1).
The contract includes real-time PCR-based tests for pathogens that include Salmonella spp., Listeria monocytogenes, Campylobacter, Escherichia coli O157:H7, and Shiga toxin producing E.
Research and development expenses of USD2.2m was announced for Q4 2015, a rise of USD0.9m over the fourth quarter of 2014 , primarily due to increased regulatory activities related to our Staph ID/R Blood Culture and Shiga Toxin Direct assays as well as growth in our development pipeline.