Case Study- Cholera

Question 1

Basic Properties of Vibrio

Answer 1

o GNB
o Oxidase POS
o Motile – single polar flagellar o Ferment glucose
o Indole POS (most of the
medically important species)

Question 2

Gram stain of Vibrio sp.

Answer 2

• Gram negative rods –

slightly curved, comma shaped

Question 3

Examples of Vibrio sp.?

Answer 3

Main human GIT pathogens Vibrio cholerae

Vibrio parahaemolyticus

Question 4

Main Symtom of Vibrio

Answer 4

Severe diarrhoea disease caused by the bacterium

Question 5

Infective does of Cholera

Answer 5

10^10orgs/ml (<100 in people with impaired gastric acid

production)

Question 6

Main problems asciotated with cholera Dehydration?

Answer 6

– loss of K+
– anuria (<50-100 mls/day)
– metabolic acidosis and shock

Question 7

Death rate of Cholera

Answer 7

Death (50-60% if untreated), <1% if treated

Question 8

Examples of the way cholera is transmitted

Answer 8

Contaminated water and foods

Question 9

People most at risk of Cholera

Answer 9

People with low gastric acid levels

Question 10

Strains of Vibrio Cholerea that cause disease?

Answer 10

O1 and O139 are toxigenic and cause epidemic cholera

Question 11

Example of countries in which cholera outbreak has occurred?

Answer 11

Haiti and Yemen

Question 12

Toxin Structure of Cholera sp.?

Answer 12

• 5 binding (B) subunits
• Active (A1) subunit
• Bridging piece (A2) links A1 to the 5B subunits

Question 13

Toxin Entry?

Answer 13

• Toxin binds to the GM1 receptor on host cells
• 5 B subunits form a pore in the host cell membrane through which the A1 unit passes
• A1 subunit is released from the toxin by reduction of the disulfide bond that links it to A2

Question 14

Vibrio cholerae - treatment?

Answer 14

• Fluid and electrolyte balance (Oral and IV)
• Antibiotic therapy
• Vaccination (not very effective)

Question 15

How to control cholera?

Answer 15

• Hygenic disposal of human faeces
• Addequate supply of drinknig water
• Good food hygiene