Cholera

Pathogen: Vibrio cholerae

• Most common in developing countries

• Gram-negative, oxidase positive, curved bacterium with a single polar flagellum → production of cholera toxin

• Cholera toxin stimulates adenylate cyclase via activation of Gs → increased cyclic AMP → increased ion (mainly chloride) and water secretion into the intestinal lumen → profuse liquid stools

Transmission

• Fecal-oral

• Undercooked seafood or contaminated water (e.g., unseparated drinking water and sewage systems)

Incubation period: 0–2 days

Infectivity

• Acid-labile (grows well in an alkaline medium)

• High infective dose required (over 108 pathogens)

• Gastric acid provides a natural barrier against V. cholerae infection; therefore, the infective dose in individuals with reduced gastric acidity is lower.

Low-grade fever, vomiting

Profuse “rice-water” stools

Dipstick (rapid test; initial test)

Stool culture (confirmatory)

Supportive therapy for gastroenteritis: Urgent initial fluids for dehydration and hypovolemia (e.g., oral rehydration solution, IV fluids)

Antibiotic therapy: Treatment should be based on culture susceptibility testing.

• Indications: severe cases

• Preferred regimen: doxycycline

• Alternative regimens

  • Azithromycin

  • OR tetracycline

  • OR trimethoprim/sulfamethoxazole

  • OR ciprofloxacin

Severe dehydration

Pneumonia may occur in children.

Cholera sicca (rare): intestinal paralysis and accumulation of liquid in the intestinal lumen → circulatory collapse and high mortality rate