Which pathotype produces toxins that disrupt fluid balance and cause watery diarrhea without invasion?

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Multiple Choice

Which pathotype produces toxins that disrupt fluid balance and cause watery diarrhea without invasion?

Watery, noninvasive secretory diarrhea is typically caused by enterotoxigenic E. coli. This pathotype makes toxins—heat-labile (LT) and heat-stable (ST)—that directly disrupt fluid balance in the intestinal lining without invading mucosal tissue. LT acts like cholera toxin, ADP-ribosylating a Gs protein to keep adenylate cyclase active, which raises cAMP and opens chloride channels, driving chloride and water into the gut lumen. ST, on the other hand, activates guanylate cyclase, increasing cGMP and also promoting water loss. The result is large volumes of watery stool produced by secretion rather than tissue invasion or inflammation. Other E. coli types involve different disease mechanisms. Enteropathogenic E. coli causes diarrhea via attaching and effacing lesions on enterocytes rather than toxin-driven fluid loss. Shiga toxin–producing E. coli damages the mucosa and often leads to bloody diarrhea and risks like hemolytic uremic syndrome. Enteroaggregative E. coli adheres in a stacked-brick pattern and can cause persistent watery diarrhea, but the hallmark here is adherence behavior and biofilm formation rather than the toxin-mediated secretory effect described.

Watery, noninvasive secretory diarrhea is typically caused by enterotoxigenic E. coli. This pathotype makes toxins—heat-labile (LT) and heat-stable (ST)—that directly disrupt fluid balance in the intestinal lining without invading mucosal tissue. LT acts like cholera toxin, ADP-ribosylating a Gs protein to keep adenylate cyclase active, which raises cAMP and opens chloride channels, driving chloride and water into the gut lumen. ST, on the other hand, activates guanylate cyclase, increasing cGMP and also promoting water loss. The result is large volumes of watery stool produced by secretion rather than tissue invasion or inflammation.

Other E. coli types involve different disease mechanisms. Enteropathogenic E. coli causes diarrhea via attaching and effacing lesions on enterocytes rather than toxin-driven fluid loss. Shiga toxin–producing E. coli damages the mucosa and often leads to bloody diarrhea and risks like hemolytic uremic syndrome. Enteroaggregative E. coli adheres in a stacked-brick pattern and can cause persistent watery diarrhea, but the hallmark here is adherence behavior and biofilm formation rather than the toxin-mediated secretory effect described.

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