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Infection - MBChB Yr 3 > Introduction to Infection - Diarrhoea > Flashcards

Introduction to Infection - Diarrhoea Flashcards

1
Q

Which bacteria are sought by routine culture of stools from patients with diarrhoea? (3)

A

Salmonella, campylobacter and E. coli O157

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2
Q

Definition of diarrhoea

A

(subjective)

An increase in fluidity and frequency of stools

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3
Q

Definition of gastroenteritis

A

Three or more loose stools in 24 hours

At least one of: fever, vomiting, pain, blood/mucus stools

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4
Q

Definition of dysentery

A

Large bowel inflammation with bloody stools

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5
Q

Describe the epidemiology of gastroenteritis (4)

A
  • Contamination of livestock/foodstuffs (due to intensive farming)
  • Poor storage of produce (i.e. not in fridge)
  • Travel related infections
  • Person-to-person spread
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6
Q

Defences against enteric infections (5)

A
  • hygiene
  • gastric acid
  • normal flora
  • gut immunity
  • gut motility
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7
Q

What are the three “types” of diarrhoea?

A
  • Non-inflammatory/secretory (e.g. cholera, travellers’ diarrhoea)
  • Inflammatory (e.g. shigella dysentry)
  • Mixed (e.g. C. difficile)
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8
Q

Describe non-inflammatory/secretory diarrhoea

A
  • Usually toxin-mediated
  • Frequent watery stools with little abdominal pain
  • Rehydration is the mainstay of treatment
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9
Q

Describe inflammatory diarrhoea

A
  • Inflammatory damage and mucosal destruction
  • Usually caused by bacterial toxin
  • Abdominal pain, bloody stools and systemic upset (fever)
    Rehydration and (sometimes) antimicrobials required
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10
Q

How long does diarrhoea due to gastroenteritis usually last?

A

<2 weeks

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11
Q

How do you assess hydration? (3)

A
  • postural blood pressure
  • skin turgor
  • pulse
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12
Q

What investigations should be done for suspected gastroenteritis?

A
  • stool culture
  • blood culture
  • renal function
  • blood count - neutrophilia, haemolysis
  • abdominal X-ray if abdomen is distended or tender
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13
Q

What is the differential diagnosis for gastroenteritis?

A
  • Inflammatory bowel disease (>2 weeks)
  • Spurious diarrhoea (secondary to constipation)
  • Carcinoma
  • Diarrhoea as part of the response to sepsis (lack of abdominal pain/tenderness and no blood/mucous in stools)
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14
Q

What is the treatment for gastro-enteritis? (3)

A
  • Rehydration (oral sugar/salt solution, or IV saline)
  • Possibly antimicrobials
  • Treatment of complications
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15
Q

What is the incubation period of campylobacter?

A

Up to 7 days (so dietary history may be unreliable)

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16
Q

What are some of the clinical features of campylobacter gastroenteritis? (4)

A
  • Severe abdominal pain
  • Rarely invades into bloodstream (<1%)
  • Clears within 3 weeks
  • Post-infection sequelae such as Guillian-Barre syndrome and reactive arthritis
17
Q

What is the typical onset and duration of symptoms of salmonella gastroenteritis?

A
  • Onset usually <48 hours after exposure

- Diarrhoea usually lasts <10 days

18
Q

What are some other clinical features of salmonella gastroenteritis? (4)

A
  • Commonest pathogens are Salmonella enteritidis and Salmonella typhimurium
  • <5% positive blood cultures
  • 20% patients still have positive stools 20 weeks post-infection
  • Post-infectious irritable bowel is common
19
Q

How does E. coli O157 infection spread?

A
  • Contaminated meat

- Person-to-person (low inoculum)

20
Q

Which symptom differentiated E. coli O157 infection from campylobacter or salmonella infection?

A

Frequent BLOODY stools

21
Q

Describe the pathogenesis of E. coli O157 gastroenteritis

A
  • E. coli O157 produces verocytotoxin(s)
  • Toxin (NOT bacteria) enters the blood
  • Can cause haemolytic-uraemic syndrome (HUS), particularly in children and the elderly
  • 5-9 days between onset of diarrhoea and HUS
22
Q

What is haemolytic-uraemic syndrome (HUS)?

A
  • Toxin causes platelet activation and micro-angiopathy

- Leads to renal failure, haemolytic anaemia and thrombocytopenia

23
Q

Which other bacteria (apart from campylobacter, salmonella and E. coli O157) can cause gastroenteritis? (7)

A
  • Shigella
  • Clostridium difficile
  • Other forms of E. coli
  • Cholera
  • Staphylococcus aureus (toxin)
  • Bacillus cereus (refried rice)
  • Clostridium perfringens (toxin)
24
Q

What are the indications for treatment of gastroenteritis with antibiotics? (5)

A
  • Immunocompromised patient
  • Severe sepsis or invasive infection
  • Valvular heart disease
  • Chronic illness
  • Diabetes
25
Q

Which bacteria typically cause travellers’ diarrhoea?

A

Enterotoxigenic E. coli

26
Q

What are the “4C antibiotics” typically associated with Clostridium difficile diarrhoea?

A

Cephalosporins
Co-amoxiclav
Clindamycin
Ciprofloxacin

(also possibly clarithromycin)

27
Q

What are possible treatments for C. difficile diarrhoea? (4)

A
  • Metronidazole
  • Oral vancomycin
  • Stool transplants
  • Surgery
28
Q

What are the common parasites which cause diarrhoea in the UK?

A
  • Giardia lamblia (diarrhoea, malabsorption)
  • Cryptosporidium parvum (no treatment)
  • Entamoeba hystolitica (amoebic dysentery - “anchovy pus” liver abscess)
29
Q

What is the most common viral enteropaths?

A

Rotavirus and norovirus

Infection - MBChB Yr 3 (14 decks)

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