Outbreak in Texas said to have been caused by shiga-toxins
Texas health officials are investigating an outbreak that has already resulted in one death, apparently caused by a Shiga toxin carried by bacteria. KEYE TV reported today that in addition to four cases in Bastrop County, Lee and Fayette Counties have reported illnesses caused by a Shiga toxin-producing bacterium.
E. coli O157:H7 and other bacteria contain Shiga toxins, and can cause severe illness, including hemolytic uremic syndrome. The chain of events leading to HUS begins with ingestion of Shiga toxin producing E. coli (e.g., E. coli O157: H7) or another Shiga toxin producing bacteria in contaminated food, beverages or through person to person transmission. These E. coli rapidly multiply in the intestines causing colitis (diarrhea), and tightly bind to cells that line the large intestine. This snug attachment facilitates absorption of the toxin into the circulation where it becomes attached to weak receptors on white blood cells (WBC) thus allowing the toxin to “ride piggyback” to the kidneys where it is transferred to numerous avid (strong) Gb3 receptors that grasp and hold on to the toxin. Organ injury is primarily a function of Gb3 receptor location and density. Receptors are probably heterogeneously distributed in the major body organs, and this may explain why some patients develop injury in other organs (e.g., brain, pancreas).
Once Shiga toxin attaches to receptors, it moves into the cell’s cytoplasm where it shuts down the cells’ protein machinery resulting in cellular injury and/or death. This cellular injury activates blood platelets and the coagulation cascade which results in the formation of clots in the very small vessels of the kidney resulting in acute kidney injury and failure. The red blood cells are hemolyized (destroyed) by Shiga toxin and/or damaged as they attempt to pass through partially obstructed microvessels. Blood platelets (required for normal blood clotting), are trapped in the tiny blood clots or are damaged and destroyed by the spleen.
Read more about Shiga toxin-induced HUS here.
