BCM 312: Clinical Biochemistry of Cholera and HIV

Cholera

• Caused by the bacterium Vibrio cholerae

History of Cholera

• El Tor biotype of V. cholerae first isolated in 1905
• Seven cholera pandemics have occurred since 1817

Epidemics

• 1992 epidemic in Madras, India caused by serogroup O1
• Seventh pandemic of cholera began in 1961 in Indonesia, Sulawesi

Characteristics of V. cholerae

• Size range: 1-3 μm x 0.2-0.5 μm
• Antigenic structure: lipopolysaccharide (LPS) and polysaccharide capsule

Pathogenesis of V. cholerae Infection

• Dramatic increase in cAMP levels within the cell caused by ADP-ribosylation of Gsα
• Sustained activation of adenylate cyclase leads to increased cAMP production
• cAMP enhances Cl- secretion and inhibits Na+ absorption, leading to secretory diarrhea
• B subunits of the toxin bind to GM1 receptor on epithelial cells lining the gut

Pathogenicity

• Presence of ctx and zot genes responsible for separating V. cholerae into pathogenic and nonpathogenic strains

Clinical Manifestations

• Net fluid loss leading to watery diarrhea caused by increased Cl- secretion and inhibited Na+ absorption
• Decreased sodium influx into the cell due to inhibition of NHE by cAMP
• V. cholerae secretes cholera toxin in the small intestine of affected individuals

This quiz covers the biochemistry of cholera, including its etymology, causative agent V. cholerae, major biotypes, and epidemiology. It also includes background information about the discovery of V. cholerae and the history of cholera pandemics. Additionally, the quiz delves into the biochemistry of HIV.