BCM 312: Clinical Biochemistry of Cholera and HIV
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BCM 312: Clinical Biochemistry of Cholera and HIV

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Questions and Answers

Which bacterium is responsible for causing cholera?

Vibrio cholerae

When was the El Tor biotype of V cholerae first isolated?

1905

How many cholera pandemics have occurred since 1817?

7

Which serogroup caused the epidemic of cholera in Madras, India in October 1992?

<p>0139</p> Signup and view all the answers

Where did the seventh pandemic of cholera begin in 1961?

<p>Indonesia</p> Signup and view all the answers

Why is the number of cholera patients worldwide uncertain?

<p>Most cases go unreported</p> Signup and view all the answers

What is the size range of the V. cholerae organism?

<p>1-3 mm in length by 0.5-0.8 mm in diameter</p> Signup and view all the answers

What is the antigenic structure of the V. cholerae organism?

<p>Flagellar H antigen and somatic O antigen</p> Signup and view all the answers

What causes the dramatic increase in cAMP levels within the cell in V. cholerae infection?

<p>ADP-ribosylation of the Gs α subunit by the toxin</p> Signup and view all the answers

What is the consequence of the sustained activation of adenylate cyclase in V. cholerae infection?

<p>Dramatic increase in cAMP levels within the cell</p> Signup and view all the answers

What is the role of cAMP in V. cholerae infection?

<p>Activates cAMP-dependent protein kinase (protein kinase A, PKA)</p> Signup and view all the answers

Which receptor do the B subunits of the toxin bind to on the epithelial cells lining the gut?

<p>Ganglioside receptor GM1 (GM1)</p> Signup and view all the answers

What is responsible for separating V. cholerae into pathogenic and nonpathogenic strains?

<p>Antigenic structure consisting of a flagellar H antigen and a somatic O antigen</p> Signup and view all the answers

What causes net fluid loss leading to watery diarrhea in V. cholerae infection?

<p>Decrease in chloride and bicarbonate movement out of the cell</p> Signup and view all the answers

What causes a decrease in sodium influx into the cell during V. cholerae infection?

<p>Increase in chloride and bicarbonate movement out of the cell</p> Signup and view all the answers

What is secreted by V. cholerae in the small intestine of affected individuals?

<p>Toxin consisting of an active A subunit attached to a ring of five B subunits</p> Signup and view all the answers

Study Notes

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

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