Infective Gastro Flashcards Preview

Hugh's MD1 Abdominal > Infective Gastro > Flashcards

Flashcards in Infective Gastro Deck (63):
1

What are the common aetiological causes of travellers diarrhoea?

ETEC, other bac. viruses and protozoa

1

What diagnotic techniques are commonly used to identify bacteria?

Culture

 

2

What are the aetiological agents responsible for dysentery?

Shigella, EIEC and protozoa (Entamoeba histolytica)

3

What the most common parasitic causes of diarrhoea in the developed world?

Giardia and crytosporidium

3

What is dysentery characterised by?

Blood, mucus and pus in the stool - more than just severe diarrhoea!

3

What is the problem with anti-motility agents?

They stop peristalsis which is a defense mechanism for the removal of pathogens.

4

What type of pathogen is the most common cause of diarrhoea in the developing world?

Bacteria

4

What diagnostic techniques are most commonly used to identify viruses?

Nucleic acid identification

Antigen detection

(Microscopy)

4

Why is oral rehydration preferable to intravenous in children?

Doesn't require a highly skilled paediatrician to insert the needle

5

How do some mothers in developing countries contribute to gastro malnutrition?

They stop breast feeding as they think the milk might be the cause of the problem. 

6

What type of E. coli produce shiga toxin?

EHEC (enterohaemorrhagic E. coli)

EAEC if it acquires a plasmid for it

6

What does EPEC stand for? What symptoms does it cause?

Enteropathogenic E. coli

Non-specific gastro in children in LDCs

7

What are the two ways diarrhoea kills people?

Immediate phase due to water and electrolyte imbalance

Delayed: mainly due to malnutrition due to enterocyte damage

7

What is the limitation with culturing faeces?

Generally only pathogens that are easy to find are looked for...

9

What happens if more than 4-5L of fluid enters the colon?

The excess is excreted as diarrhoea

10

What level of invasiveness is EPEC in terms of its diarrhoea causing ability?

Adhesive with brush border damage (destroy microvilli)

11

What is the function of Tir protein in EPEC infection?

Tir is secreted by the type III secretion sytem into enterocytes cytoplasm where is finds its way to the lumen membrane and acts as a receptor for intimin

12

How does diarrhoea contribute to malnutrition?

Increased nutrient/energy loss 

 

Reduced energy intake (malabsorption, withholding of food)

12

Of the 5 variants of pathogenic E. coli that cause GI symptoms, which cause severe disease?

EHEC - bloody diarrhoea

EIEC - dysentery

13

Shiga toxin is associated with which clinical conditions?

Haemorrhagic colitis

Haemolytic-uremic syndrome

14

What are three classes of anti-diarrhoeal drugs?

Anti-motility agents

Anti-secretory agents

Binding agents

15

Why don't animals infected with EHEC get as sick?

They have shiga toxin receptors that absorb the toxin

16

How does Salmonella manage to systemically invade?

Remains in macrophages

16

Of the 5 variants of pathogenic E. coli that cause GI symptoms which cause milder disease?

EPEC

EAEC

ETEC

16

What diagnostic techniques are commonly used to identify parasites?

Microscopy

Antigen detection

(detection of nucleic acids)

16

What is pathotyping? For what pathogen/s is it important?

Determination of virulence factors

E. coli

Yersinia

18

What causes enteric fever?

Salmonella Typhi and S. Paratyphi

19

What does EAEC stand for? What symptoms does it cause?

Enteroaggregative E. coli

Watery diarrhoea in childrens in LCDs

20

What is the function of Intimin protein in EPEC infection?

Intimin is an attachment protein EPEC uses to mediate intimate adhesion with enterocytes. It binds to Tir, a receptor also produced by EPEC

22

T/F Shigella has no animal reservoir

True

22

For what pathogen is serotyping important?

Salmonella 

22

What are some strategies against traveller's diarrhoea?

Reduce exposure to infectious agent

Immunisation

(Antimicrobials)

23

T/F Using antibiotics for cholera infection has no effect

False, it shortens the illness and infectious period

25

Where is the most fluid absorbed?

Duodenum and jejunum. 

26

What species of Shigella causes the most severe dysentery?

S. dysenteriae

28

What does ETEC stand for? What symptoms does it cause?

Enterotoxigenic E. coli 

Causes watery diarrhoea (in young children and travellers in LDCs)

29

Apart from cholerae what causes Cholera-like diarrhoea?

ETEC - discovered in soilders

31

What is haemorrhagic colitis? What causes it?

Blood in the stool (not pus)

EHEC

32

What percentage of under 5 deaths are due to malnutrition?

33%

33

How do you treat diarrhoea?

Replace fluids - most important

Reduce fluid loss - less important

34

How much fluid do we secrete from the GIT each day?

100mL

35

Entaemoba histolytica containing what thing indicates it's the cause of dysentery?

RBCs

37

Which diarrhoea causing bacteria invade the submucosa?

Salmonella, Campylobacter

38

What does seeing trophozoites of Giardia lamblia in diarrhoea stool samples indicate?

That Giardia isn't causing the diarrhoea because only the cyst stage is release in stool in normal Giardia infection. The presence of trophozoites indicates that there is another cause of diarrhoea that is forcing immature Giardia down the GIT prematurely. 

39

What is the principle of binding agents?

Attach a toxin's receptors to sand so that the toxin is absorbed in the gut

41

T/F Bacteria is the major cause of diarrhoea in the developed world.

False, viruses are!

42

What does EIEC stand for? What symptoms does it cause?

Enteroinvasive E. coli

Dysentery, any age, mainly LDCs

43

Clostridium difficile is the major cause of what diarrhoeal syndrome?

Antiboitic-associated colitis

44

T/F V. Cholerae and Shigellae are both found in the environment

False, only Cholerae is found in the environment

46

Which of the 5 E. coli utilise type III secretion systems?

EPEC and EHEC

47

Has does glucose increase fluid uptake?

It is co-transported into villus cells with Na creating an osmotic gradient for water to travel down

48

T/F Type III secretion systems are found in pathogens only

True

50

What is the pattern of diarrhoea when there is malaborption in the colon?

Frequent events of low volume

52

The causes of foodborne diarrhoea include...

Staph, Salmonella, Clostridium, Bacillus, Vibrio, Listeria, viruses (eg Norovirus), ciguatoxin

53

What are 4 virulence factors?

Adhesions factors

Endotoxins

Avoidance of immune responses

Invasive ability

54

When should antiboitics be used in the treatment of diarrhoea?

Cholera

Systemic spread of infection eg typhoid fever

Immunocompromised patients

Severe shigella infections

Protozoal infections (even if carrier only)

Pseudomembranous colitis if severe

55

What is the most important ingredient in rehydration salts?

Glucose

57

How much fluid does the colon usually absorb? What is the maximum it can absorb?

1.4L and 4-5L

59

Why is the name non-specific gastroenteritis inaccurate?

Because it refers to symptoms of diarrhoea and vomiting only and does not include actual inflammation in the GIT

60

Which virus' virion is smaller: Rotavirus, Norovirus or enteric adenovirus?

Norovirus at 30nm

The others are 70nm

61

T/F bacteria are present in amoebic dysentery

False, the amoebae eat the bacteria

62

Clostridium is a ...

Gram positive rod

Forms endospores

Strictly anaerobic

 

63

How many species of dysentery causing Shigella are there?

4