Cholera

Introduction. 

Cholera is a severe form of gastroenteritis caused by the curved bacterium Vibrio cholerae. Transmission is primarily through contaminated water sources and through consumption of undercooked shellfish. V. cholerae has several virulence factors, including pili to adhere to the intestinal lining and cholera toxin to cause intestinal cells to hypersecrete fluid. (CTx activates a G-protein, which in turn activates adenylate cyclase. AC overproduces cyclic AMP, which is responsible for opening chloride ion channels in the plasma membrane. Once chloride is able to leave the cell, sodium and water follow). Severe diarrhea (up to 1 liter per hour at the peak) results.

Immunity is short-lived, making vaccines impractical. But, since the ID50 for cholera is high, good hygiene is sufficient for healthy individuals.

Summary

• Cause: Vibrio cholerae (esp. strains O1 and O139)
• Microscopy: Gram-negative curved rods
• Transmission: Fecal-oral route (contaminated water, contaminated shellfish)
• Symptoms: Profuse watery diarrhea (rice-water stools)
• Complications: Dehydration and death in untreated esp. children
• Pathogenesis: Cholera toxin (strains O1 and O139) activates hypersecretion of electrolytes and fluid; other enterotoxins cause diarrhea in non-O1/O139 strains; pili for adhesion
• Treatment: Fluid replacement, tetracycline/doxycycline

Links

• 1. https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1004787
• 2. https://microbewiki.kenyon.edu/index.php/Cholera