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Hugh's MD1 Abdominal > Infective Gastro > Flashcards

Infective Gastro Flashcards

1
Q

What are the common aetiological causes of travellers diarrhoea?

A

ETEC, other bac. viruses and protozoa

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1
Q

What diagnotic techniques are commonly used to identify bacteria?

A

Culture

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2
Q

What are the aetiological agents responsible for dysentery?

A

Shigella, EIEC and protozoa (Entamoeba histolytica)

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3
Q

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

A

Giardia and crytosporidium

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3
Q

What is dysentery characterised by?

A

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

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3
Q

What is the problem with anti-motility agents?

A

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

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4
Q

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

A

Bacteria

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4
Q

What diagnostic techniques are most commonly used to identify viruses?

A

Nucleic acid identification

Antigen detection

(Microscopy)

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4
Q

Why is oral rehydration preferable to intravenous in children?

A

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

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5
Q

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

A

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

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6
Q

What type of *E. coli *produce shiga toxin?

A

EHEC (enterohaemorrhagic E. coli)

EAEC if it acquires a plasmid for it

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6
Q

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

A

Enteropathogenic E. coli

Non-specific gastro in children in LDCs

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7
Q

What are the two ways diarrhoea kills people?

A

Immediate phase due to water and electrolyte imbalance

Delayed: mainly due to malnutrition due to enterocyte damage

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7
Q

What is the limitation with culturing faeces?

A

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

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9
Q

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

A

The excess is excreted as diarrhoea

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10
Q

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

A

Adhesive with brush border damage (destroy microvilli)

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11
Q

What is the function of Tir protein in EPEC infection?

A

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

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12
Q

How does diarrhoea contribute to malnutrition?

A

Increased nutrient/energy loss

Reduced energy intake (malabsorption, withholding of food)

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12
Q

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

A

EHEC - bloody diarrhoea

EIEC - dysentery

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13
Q

Shiga toxin is associated with which clinical conditions?

A

Haemorrhagic colitis

Haemolytic-uremic syndrome

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14
Q

What are three classes of anti-diarrhoeal drugs?

A

Anti-motility agents

Anti-secretory agents

Binding agents

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15
Q

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

A

They have shiga toxin receptors that absorb the toxin

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16
Q

How does Salmonella manage to systemically invade?

A

Remains in macrophages

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16
Q

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

A

EPEC

EAEC

ETEC

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16
Q

What diagnostic techniques are commonly used to identify parasites?

A

Microscopy

Antigen detection

(detection of nucleic acids)

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16
Q

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

A

Determination of virulence factors

  • E. coli*
  • Yersinia*
18
Q

What causes enteric fever?

A

Salmonella Typhi and S. Paratyphi

19
Q

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

A

Enteroaggregative E. coli

Watery diarrhoea in childrens in LCDs

20
Q

What is the function of Intimin protein in EPEC infection?

A

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

22
Q

T/F Shigella has no animal reservoir

A

True

22
Q

For what pathogen is serotyping important?

A

Salmonella

22
Q

What are some strategies against traveller’s diarrhoea?

A

Reduce exposure to infectious agent

Immunisation

(Antimicrobials)

23
Q

T/F Using antibiotics for cholera infection has no effect

A

False, it shortens the illness and infectious period

25
Q

Where is the most fluid absorbed?

A

Duodenum and jejunum.

26
Q

What species of Shigella causes the most severe dysentery?

A

S. dysenteriae

28
Q

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

A

Enterotoxigenic E. coli

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

29
Q

Apart from cholerae what causes Cholera-like diarrhoea?

A

ETEC - discovered in soilders

31
Q

What is haemorrhagic colitis? What causes it?

A

Blood in the stool (not pus)

EHEC

32
Q

What percentage of under 5 deaths are due to malnutrition?

A

33%

33
Q

How do you treat diarrhoea?

A

Replace fluids - most important

Reduce fluid loss - less important

34
Q

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

A

100mL

35
Q

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

A

RBCs

37
Q

Which diarrhoea causing bacteria invade the submucosa?

A

Salmonella, Campylobacter

38
Q

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

A

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
Q

What is the principle of binding agents?

A

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

41
Q

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

A

False, viruses are!

42
Q

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

A

Enteroinvasive E. coli

Dysentery, any age, mainly LDCs

43
Q

*Clostridium difficile *is the major cause of what diarrhoeal syndrome?

A

Antiboitic-associated colitis

44
Q

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

A

False, only Cholerae is found in the environment

46
Q

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

A

EPEC and EHEC

47
Q

Has does glucose increase fluid uptake?

A

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

48
Q

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

A

True

50
Q

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

A

Frequent events of low volume

52
Q

The causes of foodborne diarrhoea include…

A

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

53
Q

What are 4 virulence factors?

A

Adhesions factors

Endotoxins

Avoidance of immune responses

Invasive ability

54
Q

When should antiboitics be used in the treatment of diarrhoea?

A

Cholera

Systemic spread of infection eg typhoid fever

Immunocompromised patients

Severe shigella infections

Protozoal infections (even if carrier only)

Pseudomembranous colitis if severe

55
Q

What is the most important ingredient in rehydration salts?

A

Glucose

57
Q

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

A

1.4L and 4-5L

59
Q

Why is the name non-specific gastroenteritis inaccurate?

A

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

60
Q

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

A

Norovirus at 30nm

The others are 70nm

61
Q

T/F bacteria are present in amoebic dysentery

A

False, the amoebae eat the bacteria

62
Q

Clostridium is a …

A

Gram positive rod

Forms endospores

Strictly anaerobic

63
Q

How many species of dysentery causing *Shigella *are there?

A

4

Hugh's MD1 Abdominal (21 decks)

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