Flashcards in Diarrhoeal Disease Deck (50)
What are the different causes of Diarrhoea?
Viral (rotavirus, norovirus)
Protozoa (Giardia, etc)
non-infectious (Coeliac disease, lactose-intolerance, etc)
What are the three main types of bacteria that cause diarrhoea?
• Vibrio cholerae
• Campylobacter jejuni!
• Clostridium difﬁcile!
What are the three types of diarrhoea?
• acute watery diarrhoea
• acute bloody diarrhoea
• persistent diarrhoea
Describe the duration and how acute water diarrhoea is caused?
lasts several hours or days,
and includes disease caused by Vibrio cholerae, Escherichia coli and Rotavirus
How and by what is acute bloody diarrhoea caused?
also called dysentery-
mainly caused by Shigella- often a result of tissue
Describe the duration and how persistant diarrhoea and what it causes?
– lasts 14 days or longer- a
major cause of malnutrition in children
What doeas Vibrio cholerae microbiology?
• Gram-negative, comma-shaped bacterium
• Flagellum at one cell pole!
What is the source, reservoir, transmission of V. cholerae?
Associated with shellfish
Lack of sanitation when disasters occur i.e. human faeces in water
Need a high dose for infections to occur (10^4 - 10^6)
Is V.cholerae prevelant in nz?
no. However there are 5 million cases around the world a year
How does V.cholerae colonize and become virulent? i.e. how does it work to cause the disease?
Large doses allow some cholerae to survive the stomach and small intestine using the pilus.
They then secrete the cholera toxin which only the virulent strains can do.
How does the cholera toxin cause the disease?
The toxin = A and B = AB5 family toxin
A = 1 subunit
B = 5 subunits only bind to enterocytes
So B binds to enterocytes and the cell endocytoses the whole toxin.
The toxin goes to endosome, Golgi then ER.
ER releases the A subunit which is an enzyme that stimulates the adenylate cyclase converting ATP to cAMP.
cAMP activates Cl- channels causing the efflux of Cl-. Na+ follows the gradient creating an osmotic IMBALANCE causing water to leave the cell and enter the gut lumen resulting in DIARRHOEA.
What are two important characterics of V.cholera disease?
It causes deregulation i.e. osmotic imbalance but DOES NOT cause cellular damage.
There is no inflammation
no physical damage to the epithelial cells in the gut.
RECOVERY is quick
What are the symptoms of V.Cholera?
Rice water stools (20L/day)
Headache due to thick blood when severe
Dehydration leading to shock
In moderate dehydration regarding V.cholera what are the symptoms?
decreased urine output
In severe dehydration regarding V.cholera what are the symptoms?
* Lack of sweating
* Little or no urination — any urine that is produced will be dark yellow or amber !
* Sunken eyes
* Shriveled and dry skin that lacks elasticity and doesn't "bounce back" when pinched into a fold
* Low blood pressure
* Rapid heartbeat
* Rapid breathing
How do you treat a moderate dehydration due to v.cholera?
How do you treat severe dehydration due to v.cholera?
Oral rehydration salts solution
mixute of clean water, salt and sugar which is absorbed replacing lost water
Which antibiotic should be used for severe and maybe moderate cases?
Why is doxycycline effective?
* Cheap, effective antibiotic against V. cholerae!
* Kills bacteria
* Reduces duration of symptoms
* Reduces shedding
* In an epidemic this reduces pressure on water for
rehydration and reduces numbers of bacteria shed into the local environment!
* Use after vomiting phase has ended
Case Numbers = Campylobacter
Case Numbers = Salmonella
Case Numbers = Shigella
Case Numbers = VTEC
Case Numbers = Yersinia
How do you kill campylobacter on a daily basis?
cooking meat well
What is the incubation period of campylobacter
What is the duration of the disease caused by campylobacter?
3 days to 3 weeks
What are the symptoms of campylobacter?
* Diarrhoea, sometimes bloody
* Abdominal cramps
* Sometimes bacteraemia – particularly in neonates and
* death is rare - mainly in infants
How does campylobacteriosis work?
Small dose, don't have endospores killed by heat.
they work by having several virulence factors i.e. lipooligosacchaide which is proinflammatory
Capsule for immune evasion
CDT - cytolethal distending toxin that leads to cell death