Vibrio Cholera

Question 0

How does one select for V.cholera in the lab?

Answer 0

Grow in an alkaline environment to select out from other faecal flora.

Question 1

Lab characteristics of V.cholera?

Answer 1

Short curved (comma-shaped)
highly motile
gram negative

Question 2

What is the serotype of V.cholera involved in disease and what can this serotype be further divided into?

Answer 2

O1 serotype:

• classical biotype
• El Tor biotype

Question 3

Difference between the V.cholera biotypes?

Answer 3

Classical - half of infected are asymptomatic

El Tor - only 1/20-100 people symptomatic

Question 4

How is V.cholera spread?

Answer 4

FAECAL-ORAL ROUTE
Unchlorinated water.
Bad sanitation 
Refugee camps 
Natural disasters 
Shellfish - can survive in slightly saline environment

Question 5

Name another V.cholera strain other than the O1 strain.

Answer 5

O139

Question 6

Why is a large innocuous of V.cholera needed to cause Diarrhoea?

Answer 6

Most bacteria are killed off by the hydrochloride acid in the stomach.
*hypochlorhydria decreases infective dose

Question 7

Outline V.cholera pathogenesis.

Answer 7

Organisms multiply in small intestine > attach to mucosal cells > release exotoxins (an enterotoxin)

Question 8

Structure of the V.cholera exotoxin? Function of each subunit?

Answer 8

Central A subunit:
- activates adenylcyclase > increase in cAMP > efflux water/electrolytes
B-subunit:
- 5 of them > involved in binding to cell + delivery of A-subunit into cell
*enterotoxin activity continues until effected cell is desquamated

Question 9

Incubation period of V.cholera?

Answer 9

2-3 days.

Question 10

Clinical manifestations of V.cholera?

Answer 10

Profuse watery Diarrhoea. RICE-WATER STOOLS.
projectile vomiting.
Muscle cramps.

Question 11

What does Diarrhoea due to V.chloera lead to?

Answer 11

Dehydration and metabolic alkalosis.

Question 12

What is infection with the El Tor biotype of V.cholera like? What does this mean for spread of this biotype?

Answer 12

Most people asymptomatic.
Symptoms mild if present.
*patients not incapacitated by illness therefore more opportunity to spread to others

Question 13

What is stupor?

Answer 13

A condition of near unconsciousness, with apparent mental inactivity and reduced ability to respond to stimulation.

Question 14

How does one diagnose cholera?

Answer 14

Faeces/vomitus sent for culture.
*must say cholera is suspected as routine stool culture does not include selective media required for isolation of vibrios.

Question 15

What considerations one take into account when sending stool/vomitus for diagnosis of cholera?

Answer 15

Specimens collected before antibiotic therapy.
Specimens transported to lab quickly as V.cholera is sensitive to drying, sunlight, and acid pH create by normal gut flora.
*special transport medium

Question 16

Treatment of cholera?

Answer 16

Replacement of lost water and electrolytes.
ORS
Antibiotics:
- decrease fluid loss and shorten the excretion of vibrios

Question 17

Antibiotics used against cholera?

Answer 17

Tetracyclines
Quinolones
*antibiotic resistance emerging

Question 18

How to prevent cholera?

Answer 18

Chlorinate or boil water
Sanitation
Hygiene
Moore-pads in surveillance (early identification)
Sari!

Question 19

Is there a vaccine against V.cholera?

Answer 19

Yes.

Toxin-A genes deleted > live attenuated strain