We have already heard from several families whose children have developed hemolytic uremic syndrome (HUS) after contracting E. coli O157:H7 from Nestle cookie dough. Most often, though we certainly see cases where the pathalogic process described below affects other organs, HUS affects the kidneys. Here is a short explanation of what HUS is, and why it is so lethal.
The toxins that are released by E. coli O157:H7 bacteria (called shiga-toxins) are so potent, in fact lethal, that the Department of Homeland Security lists it as a potential bioterrorist agent. (Although E. coli O157:H7 are responsible for the majority of cases in America, there are many additional shiga-toxin producing E. coli that can cause HUS.
The chain of events leading to HUS begins with ingestion of E. coli 0157: H7 bacteria in contaminated food. 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, or other organs, 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-toxins 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.