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Flashcards in Diarrhoeal Disease Deck (50)
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1

What are the different causes of Diarrhoea?

Bacteria

Viral (rotavirus, norovirus)

Protozoa (Giardia, etc)

Fungal (mycotoxins)
non-infectious (Coeliac disease, lactose-intolerance, etc)

2

What are the three main types of bacteria that cause diarrhoea?

•  Vibrio cholerae
•  Campylobacter jejuni!
•  Clostridium difficile!

3

What are the three types of diarrhoea?

•  acute watery diarrhoea
•  acute bloody diarrhoea
•  persistent diarrhoea

4

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

5

How and by what is acute bloody diarrhoea caused?

also called dysentery-
mainly caused by Shigella- often a result of tissue
invasion

6

Describe the duration and how persistant diarrhoea and what it causes?

– lasts 14 days or longer- a
major cause of malnutrition in children

7

What doeas Vibrio cholerae microbiology?

•  Gram-negative, comma-shaped bacterium
•  Flagellum at one cell pole!

8

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)

9

Is V.cholerae prevelant in nz?

no. However there are 5 million cases around the world a year

10

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.

11

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.

12

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

13

What are the symptoms of V.Cholera?

Vomiting (1-2L/day)
Rice water stools (20L/day)
Headache due to thick blood when severe
Dehydration leading to shock
NON-BLOODY stools

14

In moderate dehydration regarding V.cholera what are the symptoms?

tired
thirsty
decreased urine output
dry skin
headache

15

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

16

How do you treat a moderate dehydration due to v.cholera?

good hygiene
intravenous fluid
improved sanitation

17

How do you treat severe dehydration due to v.cholera?

intravenous fluid
Oral rehydration salts solution
mixute of clean water, salt and sugar which is absorbed replacing lost water
antibiotics

18

Which antibiotic should be used for severe and maybe moderate cases?

Doxycycline

19

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

20

Case Numbers = Campylobacter

6708, 153.6

21

Case Numbers = Salmonella

1178, 27

22

Case Numbers = Shigella

101, 2.3

23

Case Numbers = VTEC

163, 3.7

24

Case Numbers = Yersinia

423, 9.7

25

How do you kill campylobacter on a daily basis?

cooking meat well

26

What is the incubation period of campylobacter

2-11 days

27

What is the duration of the disease caused by campylobacter?

3 days to 3 weeks

28

What are the symptoms of campylobacter?

* Diarrhoea, sometimes bloody
* Abdominal cramps
* Fever
* Sometimes bacteraemia – particularly in neonates and
compromised adults
* death is rare - mainly in infants

29

How does campylobacteriosis work?

Small dose, don't have endospores killed by heat.
BUT
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

30

What do campylobacter look under the microscope?

* darkfield or phase-contrast microscopy of faecal
specimens demonstrates the characteristic darting

* Gram stain of the stool show slim, short (0.3-0.6 µm), curved rods.
* cultured on Selective and discriminative agars. Look like watery drops on agar plates