Vibrio cholerae Overview and Pathogenesis

Vibrio cholerae Overview

• Gram-negative, oxidase-positive, motile rod-shaped bacteria
• Salt-tolerant or salt-requiring
• Found in freshwater ponds and brackish water
• Cultivable on standard stool culture media
• Causes cholera disease

Transmission

• Transmitted by the fecal-oral route (contaminated food/water)
• Large infectious dose required; person-to-person transmission is less common
• Recovered cholera patients can shed the bacteria, acting as reservoirs in endemic areas

Pathogenesis

• Incubation period: 6 hours to 3 days
• Adheres to intestinal microvilli after crossing the stomach acid barrier
• Multiplies, producing potent cholera toxin (enterotoxin)
• Toxin acts on GM1 ganglioside receptors on intestinal cells
• Cholera toxin's A1 subunit activates adenylate cyclase
• Activates adenylate cyclase, increasing intracellular cAMP
• This leads to sodium, potassium, and chloride loss (Hypersecretion of Cl− and HCO3−)
• Water and electrolytes lost in stool (rice-water stool), leading to dehydration, acidosis, and shock

Clinical Findings

• Sudden vomiting
• Profuse watery diarrhea (rice-water stool) with abdominal cramps
• Rapid fluid loss and electrolyte depletion causing dehydration, circulatory collapse, and anuria
• High mortality rate (25-50%) without treatment

Diagnosis

• Stool or vomitus culture

Treatment

• Fluid and electrolyte replacement therapy
• Effective antimicrobial therapies (e.g., oral tetracycline)

Prevention

• Improved public sanitation to reduce fecal contamination of water sources
• Avoiding contaminated food/water
• Boiling drinking water
• Handwashing
• Vaccination is short-term in providing protection.