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Year 2 - GI System > Enteric Infection - Infectious Diarrhoea > Flashcards

Enteric Infection - Infectious Diarrhoea Flashcards

1
Q

Name three pathogenic mechanisms of an enteric infection.

A

Toxin mediated
Damage to intestinal epithelial surface
Invasion across intestinal epithelial barrier

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2
Q

Name some bacteria that have a toxin mediated pathogenic mechanism of causing diarrhoea.

  • produced prior to consumption
  • produced after consumption
A

Prior - S.aureus and B.cereus

After - C.diff and E.coli

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3
Q

What bacteria and what virus can cause vomiting within 6-12 hours of consuming food?

A

S.aureus and B.cereus - because if symptoms set in this quick, then the bacteria must be preformed
Norovirus

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4
Q

Describe the diarrhoea most commonly produced when the small intestine is affected.

A

Large volumes of watery diarrhoea
Causes cramps, bloating, wind and weight gain
Fever and blood in the stool is rare

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5
Q

Describe the diarrhoea most commonly produced when the large intestine is affected.

A

Frequents, small volumes of painful stool

Fever and blood is common

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6
Q

What are the main causes of bacterial diarrhoea?

- list some less common if you can

A 
S.aureus
B.cereus
E.coli
C.diff
Shigella
Salmonella
Campylobacter sporidium

Vibrio sporidium
C.perfringens
Yersinia
Plesiomonas

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7
Q

What are the main causes of viral diarrhoea?

A

Norovirus
Rotavirus
Adenovirus

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8
Q

What are the main causes of parasitic bacteria?

A 
Cryptosporidium
Giardia
Entamoeba histolytica 
Cyclospora 
Isospora
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9
Q

What four steps can help diagnose the patient?

A

History
Stool leukocytes and occult blood
Stool examination and culture
Endoscopy

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10
Q

What must you ask a patient in a diarrhoeal history?

A 
Food history
Onset and nature of symptoms 
Residence 
Occupation
Travel
Pets/hobbies
Recent hospitalisation/antibiotics 
Co-morbidity
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11
Q

Why do we look at faecal leukocytes and occult blood when diagnosing a diarrhoeal illness?

A

The presence of faecal leukocytes may indicate a colonic or ‘inflammatory’ cause
- poor sensitivity and specificity and not used clinically
Faecal occult blood can indicate a bacterial cause

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12
Q

Why do we do a stroll culture when diagnosing a diarrhoeal illness?

A

Necessary to document a pathogen

  • self liming illness
  • indicators for treatment
  • public health implications
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13
Q

When would you perform a stool microscopy during the diagnosis of a diarrhoeal illness?

A

Is a parasitic cause is possible - to look for ova and cysts

- check travellers and those whose epidemiology suggests this

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14
Q

Why would you perform an endoscopy when trying to diagnose a diarrhoeal illness?

A

To look for an alternative cause of the diarrhoea - so when the cause is unknown
- e.g. Inflammatory bowel disease or neoplastic disease

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15
Q

Describe how an oral rehydration solution works.

A

To stop diarrhoea we need to absorb more salt, in order to drag the water from the intestine, into the body.
To do this people are given a salt and water solution to ingest
It also contains glucose because salt is absorbed better in the presence of glucose - NA-glucose cotransporter

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16
Q

Name two ways in which fluid replacement treatment can be given to someone with diarrhoea.

A

Oral rehydration therapy

IV fluid

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17
Q

What are the downsides with using antibiotics in some cases?

A
  • can sometimes be self limiting
  • reduces durations by only a day
  • can worsen E.coli cases
18
Q

Who should get antibiotics?

A

Very ill patients - sepsis or evidence of bacteraemia
Those with significant comorbidity
- reducing the duration is clinically meaningful
Certain causes - C.diff associated diarrhoea (metronidazole)

19
Q

Describe the infectious dose and mechanism of invasion of campylobacter.

A

Infectious dose - around 9000 organisms
Attach to and invade the intestinal epithelial cells in both the small and large bowel
Incubation period - 3 days

20
Q

What are the clinical features of a campylobacter infection?

A

Diarrhoea - frequent, high volume, often with blood
Abdominal pain - often severe
Nausea
Fever

21
Q

How should a campylobacter infection be managed and why?

A

It should be left alone

  • self limiting (7 days)
  • high rates of antibiotic resistance
  • develops resistance on treatment
22
Q

What is the infectious dose of salmonella, and how long does it take to infect the host?

A

Around 10000 organisms

Illness within 72hrs of ingestion - but the more organisms there are, the more rapid the onset

23
Q

How does salmonella affect the intestine of the host?

A

It’s decreases stomach acid (big risk)
Diminishes the gut flora (increased risk)
Invades enterocytes with a subsequent inflammatory response

24
Q

What are the clinical features of salmonella?

A

Nausea
Diarrhoea
Abdominal cramps
Fever

25
Q

In how many cases does salmonella cause bacteraemia?

A

Less than 5%

26
Q

What is the pathogenesis and infectious load of E.coli?

A

Pathogenesis
- attachment
- Shiga toxin production - kills the enterocytes and enters systemic circulation
Infectious load can be as little as 10 organisms - with a 3-4 incubation period

27
Q

What are the clinical features of an E.coli infection?

A

Bloody diarrhoea and abdominal tenderness

Fever is rare

28
Q

E.coli can cause haemolytic uraemic syndrome in 9% of patients. What is this?

A 
Systemic effect of Shiga toxin 
It causes
- microangiopathic haemolytic anaemia
- acute renal failure 
- thrombocytopenia
29
Q

What is the treatment and mortality rate for haemolytic uraemic syndrome?

A

50% of patients need dialysis

3-5% mortality rate

30
Q

How is an E.coli infection treated and prevented?

A 
Supportive management 
Prevention 
- infection control fro health care workers 
- screening of contacts
- appropriate butchering of meat
- public health measures in outbreaks
31
Q

What are the risk factors of C.diff associated diarrhoea?

A

Antibiotic exposure
Being older than 65
PPI use
Hospitalisation

32
Q

What is the pathogenesis of C.diff associated diarrhoea?

A

It decreased colonisation resistance
The colon gets colonised
Toxins are produced

33
Q

What are the clinical features of C.diff associated diarrhoea?

A

Loose stool and colic
Fever
Leukocytes is
Protein losing enteropathy

34
Q

How can C.diff associated diarrhoea be diagnosed?

A

Antigen detection

Toxin detection

35
Q

What is the treatment for C.diff associated diarrhoea?

A

Stop causative antibiotics if possible
Metronidazole or vancomycin
Allows recolonisation with normal flora

36
Q

What is the most common cause of viral gastroenteritis?

A

Norovirus - the winter vomiting bug

37
Q

How is Norovirus transmitted and what is its infectious dose?

A

Faecal-oral route

Infectious dose is 10-100 viruses

38
Q

What are the clinical features of a Norovirus infection?

A

Acute explosive diarrhoea and vomiting lasting 24-48 hours

39
Q

Out of parasitic, viral and bacterial, which is the most common cause of infectious diarrhoea?

A

Viral

40
Q

What is the definition of diarrhoea?

A

3 or more loose or watery stools per day

Year 2 - GI System (18 decks)

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