Vibrio Cholera Flashcards
How does one select for V.cholera in the lab?
Grow in an alkaline environment to select out from other faecal flora.
Lab characteristics of V.cholera?
Short curved (comma-shaped)
highly motile
gram negative
What is the serotype of V.cholera involved in disease and what can this serotype be further divided into?
O1 serotype:
- classical biotype
- El Tor biotype
Difference between the V.cholera biotypes?
Classical - half of infected are asymptomatic
El Tor - only 1/20-100 people symptomatic
How is V.cholera spread?
FAECAL-ORAL ROUTE Unchlorinated water. Bad sanitation Refugee camps Natural disasters Shellfish - can survive in slightly saline environment
Name another V.cholera strain other than the O1 strain.
O139
Why is a large innocuous of V.cholera needed to cause Diarrhoea?
Most bacteria are killed off by the hydrochloride acid in the stomach.
*hypochlorhydria decreases infective dose
Outline V.cholera pathogenesis.
Organisms multiply in small intestine > attach to mucosal cells > release exotoxins (an enterotoxin)
Structure of the V.cholera exotoxin? Function of each subunit?
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
Incubation period of V.cholera?
2-3 days.
Clinical manifestations of V.cholera?
Profuse watery Diarrhoea. RICE-WATER STOOLS.
projectile vomiting.
Muscle cramps.
What does Diarrhoea due to V.chloera lead to?
Dehydration and metabolic alkalosis.
What is infection with the El Tor biotype of V.cholera like? What does this mean for spread of this biotype?
Most people asymptomatic.
Symptoms mild if present.
*patients not incapacitated by illness therefore more opportunity to spread to others
What is stupor?
A condition of near unconsciousness, with apparent mental inactivity and reduced ability to respond to stimulation.
How does one diagnose cholera?
Faeces/vomitus sent for culture.
*must say cholera is suspected as routine stool culture does not include selective media required for isolation of vibrios.
What considerations one take into account when sending stool/vomitus for diagnosis of cholera?
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
Treatment of cholera?
Replacement of lost water and electrolytes.
ORS
Antibiotics:
- decrease fluid loss and shorten the excretion of vibrios
Antibiotics used against cholera?
Tetracyclines
Quinolones
*antibiotic resistance emerging
How to prevent cholera?
Chlorinate or boil water Sanitation Hygiene Moore-pads in surveillance (early identification) Sari!
Is there a vaccine against V.cholera?
Yes.
Toxin-A genes deleted > live attenuated strain
