Review Question - QID 213576

This patient who is experiencing watery diarrhea from a lactose-fermenting, gram-negative organism is most likely infected by Escherichia coli. This organism produces a heat-stable enterotoxin that increased cyclic guanosine monophosphate levels.

E. coli is a common cause of diarrhea in otherwise healthy adult patients. This organism produces 2 enterotoxins that can induce a secretory diarrhea in patients. This diarrhea is generally watery with no blood in the stool. Furthermore, it will not have associated systemic symptoms such as fever since it does not invade the intestinal wall. The 2 toxins that are produced are heat-labile toxin, which increases cyclic adenosine monophosphate levels, and heat-stable toxin, which increases cyclic guanosine monophosphate levels.

Incorrect Answers:
Answer 1: Decreased cyclic adenosine monophosphate levels would be seen with increased activation of G-alpha-i signaling. This pathway is engaged by pertussis toxin but is not targeted by any E. coli toxins.

Answer 2: Decreased cyclic guanosine monophosphate is not the mechanism of action for any major bacterial toxin.

Answer 3: Increased calcium would occur with increased activation of the G-alpha-q second messenger pathway; however, this pathway is not engaged by any E. coli toxins.

Answer 4: Increased cyclic adenosine monophosphate would occur with the E. coli heat-labile toxin; however, this is not the mechanism of action for heat-stable toxin.

Bullet Summary:
Escherichia coli heat-stable toxin functions by increasing the concentration of cyclic guanosine monophosphate.