What pathogen increases Cl- secretory channels in crypt cells, causing diarrhea?

The correct answer is Vibrio cholerae. This bacterium is known for causing cholera, a disease characterized by severe diarrhea. The pathophysiology involves the production of cholera toxin, which interacts with the intestinal epithelium. This toxin activates the adenylate cyclase enzyme through the stimulation of Gs protein, leading to an increase in cyclic AMP (cAMP) levels within intestinal crypt cells.

The elevated cAMP results in the activation of protein kinase A (PKA), which subsequently increases the activity of Cl- secretory channels, such as CFTR (Cystic Fibrosis Transmembrane Conductance Regulator). This increase in Cl- secretion into the intestinal lumen draws more water into the lumen osmotically, leading to the watery diarrhea that is characteristic of cholera.

In contrast, other pathogens listed may cause gastrointestinal disturbances, but they do not primarily act by increasing Cl- channel activity in the same way as Vibrio cholerae. For instance, Escherichia coli can cause diarrhea through different mechanisms such as enterotoxigenic and enterohemorrhagic forms, but these do not specifically involve the activation of Cl- channels in crypt cells. Similarly, Salmonella typhi typically causes