For Enterotoxigenic Escherichia coli (ETEC), which statement is correct regarding its toxins?

• A. It causes traveler's diarrhea via water transmission and increases cAMP and cGMP.
• B. It produces Shiga-like toxin causing bloody diarrhea.
• C. It uses a heat-stable toxin that increases cGMP and a heat-labile toxin that increases cAMP.
• D. It is oxidase-positive.

Answer: (C)

The key idea is that ETEC causes watery traveler's diarrhea through two distinct enterotoxins that raise different intracellular messengers. The heat-labile toxin increases cyclic AMP, while the heat-stable toxin increases cyclic GMP; together they drive secretory diarrhea. The statement that matches this mechanism exactly notes both toxins and their respective effects on cAMP and cGMP. Shiga-like toxin is associated with Shiga-toxigenic E. coli and bloody diarrhea, not ETEC; oxidase status isn’t the defining feature, and focusing on the specific toxin actions on cAMP and cGMP best captures how ETEC causes disease.