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Shiga toxin (Stx) is a potent protein toxin produced by certain bacteria, primarily enterohemorrhagic Escherichia coli (such as strain O157:H7) and Shigella dysenteriae. It was first discovered by Japanese bacteriologist Kiyoshi Shiga in 1898 while studying the causative agent of dysentery, hence the name. Shiga toxins are divided into two main types: Stx1 and Stx2. STEC stands as a new foodborne and waterborne pathogen which belongs to the Escherichia coli family. The consumption of STEC bacteria results in severe health issues which can develop into hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS) that might prove fatal. STEC infection stands as the main cause of fatal foodborne bacterial diseases among children because it requires minimal amounts to cause infection and spreads easily between people. The current situation shows that no medical treatments or vaccines exist to protect against STEC infections after exposure. STEC contains two main virulence factors which are Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) that function as AB5 toxins with an enzymatically active A subunit linked to five receptor binding B subunits and function as type II ribosome-inactivating proteins (RIPs). The A subunits of Stx1 and Stx2 contain two parts: the catalytic A1 chain (residues 1-251 in Stx1 and 1-250 in Stx2) and the A2 chain (residues 252-293 in Stx1 and 251-297 in Stx2) which become separated by furin protease cleavage through a disulfide bond. The complete natural toxin exists as a single entity which scientists call the 'holotoxin'. The B subunit of the toxin recognizes globotriaosylceramide (Gb3) sugar domains on plasma membrane glycosphingolipids to enable cell entry and toxin transport into cells.
Figure 1. The structure of Shiga toxin and its receptor globotriaosylceramide (Gb3). (Engedal N, 2011)
The molecular structures of Shiga toxin 1 and 2 differ from each other while their virulence mechanisms shows better ribosome binding properties and enhanced catalytic performance which leads to higher cytotoxic effects than St and clinical disease-causing abilities also show distinct characteristics. The A1 subunit of Stx2x1. The binding process of Stx2 to ribosomes occurs at a faster rate while its depurination activity reaches higher levels which results in superior translational inhibition of both yeast and mammalian cells. The Stx2 toxin exists in at least seven different isoforms which include Stx2a, 2b and 2c. The most dangerous human disease-causing Stx2 variants include Stx2a, Stx2c and Stx2d which lead to severe conditions like hemorrhagic colitis and hemolytic uremic syndrome. The lethal dose required to kill half of mice exposed to Stx2 exceeds 100 times the dose needed for Stx1 and Stx2 produces stronger macrophage activation of IL-1β and TNFα cytokine production which may explain its increased pathogenic potential.
Figure 2. Crystallographic structures of Stx1A1 and Stx2A1 showing the electrostatic charge distribution. (Basu, 2016)
The molecular diagnostic technique Loop-mediated isothermal amplification (LAMP) stands out for detecting Stx genes (stx1/stx2) because it provides better sensitivity than PCR methods. The stx2-LAMP method achieves a detection threshold of 3.54×10⁻⁵ ng/μL which represents a 1000-fold improvement over stx2-PCR detection capabilities. The LAMP method performs complete amplification within one hour at 63°C while its results become visible through turbidity or fluorescence or colorimetric methods using hydroxynaphthol blue visualization without requiring sophisticated equipment. The multiplex LAMP technique enables simultaneous detection of stx1 and stx2 and an internal control gene with 100% accuracy. The toxin protein detection method MESI-MS/MS operates through membrane electrospray ionization mass spectrometry but LAMP remains the preferred choice for field and grassroots screening because of its fast results and affordable cost.
The medical field shows that Stx2 exists as a direct cause of hemolytic uremic syndrome (HUS). The research indicates that Stx2 infection alone leads to HUS in 23.7% of cases but the presence of Stx1 and Stx2 together reduces this risk to 12.7% and Stx1 infection alone produces no HUS risk. The binding of2. The HUS risk exceeds 50% when patients contract serotype O26 infections that contain Stx2a and Stx2c subtypes. The Stx2f subtype exists in Stx1 to Gb3 receptors creates a competitive effect that reduces the toxic activity of Stx animal reservoirs but it also leads to human infections with an estimated 19.2% chance of developing HUS. The identification and classification of Stx2 plays an essential role in determining patient outcomes and creating treatment plans.
Stuminant animals including cattle and sheep before they spread to humans through contact with contaminated environmental sources and water supplies and animal products. Research indicates that zoo deer and other wild animals carry the stx2 genex2 exists in specific distribution patterns throughout nature and its natural reservoirs. The bacteria primarily affect r in their feces which makes them potential sources of human infection. The different Stx2 subtypes show distinct geographical patterns of distribution. The Stx2a and Stx2c subtypes predominate in North American and European clinical isolates but Stx2d appears more frequently in environmental and zoonotic strains. The geographical spread of Stx2 subtypes determines the likelihood of local disease outbreaks and transmission events.
The medical field lacks any specific antiviral medications which target Stx toxins. The main treatment approach for patients involves supportive care through fluid administration and electrolyte correction and renal replacement therapy. The treatment of severe HUS patients benefits from prompt plasma exchange and eculizumab administration as complement inhibitors. The main prevention methods include proper food handling practices through meat cooking and avoiding unpasteurized dairy products and strict infection control measures in environments where risks are high such as farms and zoos. Scientists continue to develop experimental vaccines which include Stx2 subunit vaccines and toxoid vaccines that work to block toxin activity instead of removing the pathogen.
Verocytotoxigenic / Shiga toxin-producing E. coli (VTEC / STEC)
Reference
| Target | Cat. No. | Product Name | Host | |
| E. coli Verotoxin | DAGB116 | Recombinant E. coli Verotoxin II | E. coli | Inquiry |
| DAGB118 | E. coli Shiga Toxin 2 | E. coli | Inquiry | |
| DAGA-985 | Recombinant E.Coli O157:H7 Shiga Like Toxin-2 Subunit B [His] | E. coli | Inquiry | |
| DAGB117 | E. coli Shiga Toxin 1 | E. coli | Inquiry | |
| DAGA-984 | Recombinant shiga toxin-1 subunit B [His] | E. coli | Inquiry | |
| DAGA-878 | Recombinant shiga toxin 2 subunit b (aa 89,>98%) [His] | E. coli | Inquiry | |
| DAGA-877 | Recombinant shiga toxin 1 subunit b (≥95%) [His] | E. coli | Inquiry |
| Target | Cat. No. | Product Name | Size | Species | Application | Detection Sample | |
| E. coli Verotoxin | DEIA2348 | E. Coli Verotoxin (Fecal) ELISA Kit | 96T | Human | Qualitative | Stool supernatant | Inquiry |
| DEIA1966 | E. Coli Verotoxin 1+2 Ag ELISA Kit | 96T | Qualitative | Stool specimens, broth cultures | Inquiry | ||
| DEIASL162 | Shiga toxins ELISA Kit | 96T | Human | Qualitative | Fecal | Inquiry |
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