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infection > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

What is the difference between diarrhoea, gastro-enteritis and dysentery?

A

diarrhoea: fluidity and frequency (subjective)

gastro-enteritis: three or more loose stools/day + accompanying features (objective)

dysentery: large bowel inflammation + blood stools (obvious)

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2
Q

What are the 7 types of stool on the Bristol stool chart?

A
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3
Q

What are some causes of gastro-enteritis?

A
  • contamination of foods
  • poor storage of produce: bacterial proliferation at room temp
  • travel related infections: eg salmonella
  • person to person spread: eg norovirus
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4
Q

Are viruses or bacteria the most common cause of gastro-enteritis?

A

Viruses

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5
Q

Which bacteria is the commonest bacterial pathogen for gastro-enteritis?

A

Campylobacter

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6
Q

What bacteria causes the most hospital admissions due to gastro-enteritis?

A

Salmonella

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7
Q

What are some defences against enteric infection?

A
  • Hygiene
  • Stomach acidity
  • Normal gut flora
  • Immunity
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8
Q

What are the 3 classes of clinical features of diarrhoeal illness?

A
  • non-inflammatory/secretory
  • inflammatory
  • mixed
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9
Q

How do non-inflammatory/secretory illnesses cause diarrhoea?

A

secretory toxin-mediated

  • cholera increases cAMP levels and Cl secretion
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10
Q

What is an example of bacteria that causes non-inflammatory/secretory illness and diarrhoea?

A
  • enterotoxigenic E.coli (travellers diarrhoea)
  • cholera
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11
Q

What is the main therapy for a non-inflammatory/secretory illness causing diarrhoea?

A
  • Rehydration mainstay of therapy
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12
Q

What is an example of a bacteria causing inflammatory diarrhoeal illness?

A

Shigella dysentery

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13
Q

Describe how inflammatory illness causes diarrhoea?

A
  • inflammatory toxin damage and mucosal destruction causing pain and fever
  • bacterial infection/amoebic dysentery
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14
Q

What is the treatment for inflammatory illnesses causing diarrhoea?

A
  • Antimicrobials but rehydration alone is often sufficient treatment
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15
Q

Which of non-inflammatory/secretory or inflammatory illness is more associated with pain?

A

Non-inflammatory - frequent watery stools with little abdominal pain

Inflammatory - pain and fever

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16
Q

What is an example of bacteria causing diarrhoea by both non-inflammatory and inflammatory mechanisms?

A

C. Difficile

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17
Q

Describe the mechanism of diarrhoea in cholera?

A
  1. Increased cAMP results in loss of Cl from cells along with Na and K
  2. Osmotic effect leads to massive loss of water from gut
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18
Q

In what kind of diarrhoea can fluid and electrolyte loss be severe?

A

Fluid and electrolyte loss can be severe with secretory diarrhoea:

  • Hyponatraemia due to sodium loss
  • Hypokalaemia due to K loss
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19
Q

When assessing a patient with diarrhoea what should be explored?

A
  • Symptoms and duration
  • Risk of food poisoning
    • Dietary, contact, travel history
  • Assess hydration
    • Postural BP, skin turgor, pulse
  • Features of inflammation
    • Fever, raised WCC
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20
Q

What are signs of poor hydration?

A
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21
Q

What investigations should be done for diarrhoea?

A
  • Stool culture with or without molecular or Ag testing
  • Blood culture
  • Renal function
  • Blood count
    • Neutrophilia, haemolysis
  • Abdominal x-ray/CT if abdomen distended or tender
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22
Q

What is the common differential diagnosis for infectious diarrhoea?

A
  • Inflammatory bowel disease
  • Spurious diarrhoea
    • Secondary to constipation
  • Carcinoma
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23
Q

What are indicators that the diarrhoea and fever is not due to gastro-enteritis?

A

Diarrhoea and fever can occur with sepsis outside of the gut:

  • Lack of abdominal pain goes against gastroenteritis
  • No blood/mucus in stools
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24
Q

What is the treatment of gastro-enteritis?

A

Rehydration:

  • Oral rehydration with salt/sugar solution
  • IV saline
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25
Q

What is done to identify causative organism of infectious diarrhoea?

A

Routine bacterial culture is done to identify causative organism, but is difficult midst complex normal flora:

  • Takes 3 days to complete all tests
  • Selective and enrichment methods of culture necessary
    • Molecular detection
    • Antigen detection
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26
Q

What two species of coampylobacter cause the most infections?

A
  • C. Jejuni (90%)
  • C. Coli (9%)
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27
Q

Where is campylobacter found?

A

Found in chickens, contaminated milk, puppies

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28
Q

Does campylobacter gastroenteritis usually occur in isolated cases or outbreaks?

A

Isolated cases

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29
Q

Describe the timing of salmonella gastroenteritis?

A
  • Symptoms onset usually <48 hours after exposure
  • Diarrhoea usually lasts less than 10 days
30
Q

What 2 species of salmonella usually cause salmonella gastroenteritis?

A
  • S. Enterica and S. Bongori
  • >2500 serotypes with individual names, most are S. Enterica
31
Q

How is salmonella identified as the cause of gastroenteritis?

A

Screen by microscope, then antigen and biochemical tests

32
Q

What species of salmonella cause enteric fever and not gastro-enteritis?

A

S.Typhi and S.Paratyphi cause enteric fever (typhoid and parathyphoid) and not gasto-enteritis

33
Q

How is E-Coli 0157 spread?

A

Infection from contaminated meat or person to person spread

34
Q

What is an E-coli 0157 infection characterised by?

A

Characterised by frequent bloody stools

35
Q

What toxin is produced by E-coli 0157

A
36
Q

What is a consequence of toxins from E-Coli 0157 getting into the blood?

A

Toxin can cause haemolytic-uraemic (HUS) syndrome, which is haemolytic anaemia and renal failure and thrombocytopenia:

  • This happens because toxins stimulate platelet activation causing micro-angiopathy
  • Treatment is supportive, antibiotics not indicated
37
Q

What is HUS?

A

Haemolytic-uraemic syndrome:

  • which is haemolytic anaemic, renal failure and thrombocytopenia
38
Q

How do toxins from e-coli 0157 cause HUS?

A

This happens because toxins stimulate platelet activation causing micro-angiopathy

39
Q

What is the treatment for HUS?

A

Treatment is supportive, antibiotics not indicated

40
Q

What bacteria is usually responsible for diarrhoea?

A

Campylobacter

Salmonella

E. Coli 0157

Shigella

Other forms of e.coli

Staph aureus

Bacillus cereis

Clostridium perfringens

Clostridium difficile

41
Q

What 4 species of shigella are known to cause diarrhoea?

A

S. Sonnei, S. Flexneri, S. Boydii, S. Dysenteriae

42
Q

What are several forms of e.coli?

A
  • Enteropathogenic
  • Enterotoxic (travellers disease)
  • Routine diagnosis of may E. Coli strains is not possible, only 0157 as is not sorbitol fermenting whereas the rest are
43
Q

What are some occasional causes of food poisoning outbreaks?

A
  • Staph aureus (toxin)
  • Bacillus cereus
  • Clostridium perfringens
44
Q

When are antibiotics indicated in gastroenteritis?

A

Indicated in gastroenteritis for:

  • Immunocompromised
  • Severe sepsis or invasive infection
  • Chronic illness such as malignancy

Not indicated for healthy patient with non-invasive infection

45
Q

Patients with C. Diff diarrhoea usually have a history of what?

A

Patient usually has history of previous antibiotic treatment

46
Q

What is inflammation of the large intestine due to overgrowth of C. Diff called?

A

Pseudomembranous colitis

47
Q

What toxins does C. Diff produce?

A

C. Diff produces enterotoxin (A) and cytotoxin (B) which are inflammatory

48
Q

What are different forms of treatment for C. Diff diarrhoea?

A
  • Metronidazole
  • Oral vancomycin
  • Fidaxomicin (new and expensive)
  • Stool transplants
  • Surgery may be required
49
Q

What can be done for CDI prevention?

A
  • Reduction in broad spectrum antibiotic prescribing
  • Avoid 4Cs
    • Cephalosporins
    • C-amoxiclav
    • Clindamycin
    • Ciprofloxacin
  • Antimicrobial management team (AMT) and local antibiotic policy
  • Isolate symptomatic patients
  • Wash hands between patients (spores resist alcohol rubs)
  • Cleaning environment
50
Q

What does AMT stand for?

A

Antimicrobial management team

51
Q

What antibiotics should be avoided to avoid risking a C. Diff overgrowth?

A
  • Cephalosporins
  • Co-amoxiclav
  • Clindamycin
  • Ciprofloxacin
52
Q

Describe the management of CDI?

A
  • Stop precipitating antibiotics (if possible)
  • Follow published treatment algorithm
    • Oral metronidazole if no severity markers
    • Oral vancomycin if 2 or more severity markers
53
Q

What is responsible for parasite infections?

A

Protozoa and helminths

54
Q

What are parasite infections generally diagnosed by?

A

Diagnosis generally by microscopy:

  • Send stool with request “parasites, cysts and ova” or P, C and O
55
Q

What are common UK parasites?

A
  • Giardia duodenalis
  • Cryptosporidium parvum
56
Q

What does giardia duodenalis cause?

A
  • Causes diarrhoea, gas, malabsorption, failure to thrive
57
Q

What is giardia duodenalis transmitted by?

A
  • Direct contact with cattle/cats/dogs/other people
  • Food/water contaminated with faeces
58
Q

How is giardia duodenalis infection diagnosed?

A
  • Cysts seen on stool microscopy
59
Q

What is the treatment for a giardia duodenalis infection?

A
  • Treat with metronidazole
60
Q

What does cryptosporidium parvum cause?

A
  • Causes diarrhoea, nausea, vomiting and abdominal pain
61
Q

What is cryptosporidium parvum transmitted by?

A
  • Transmitted by infected animals/faeces, or food water
62
Q

How is a cryptosporidium parvum infection diagnosed?

A
  • Oocysts seen on microscopy
63
Q

What is the treatment for a cryptosporidium parvum infection?

A
  • No specific treatment usually required
64
Q

What is a common imported parasite?

A
  • Entamoeba histolytica
65
Q

What infections can entamoeba histoytica cause?

A
  • Different infections
    • Ameobic dysentery (intestinal amoebiasis)
    • Invasive extraintestinal amoebiasis (liver/pleuropulmonary/brain abscess)
66
Q

What investigations are done for entamoeba histolytica infection?

A
  • Microscopy
    • Trophozoites in symptomatic patient
    • Cysts in asymptomatic patient
  • Antibody detection (serum) for invasive disease
67
Q

What is the treatment for entamoeba histolytica infection?

A
  • Metronidazole and luminal agent to clear colonisation
68
Q

What is viral diarrhoea often caused by?

A
  • Rotavirus
    • In children under 5
  • Norovirus
    • Vaccine exists for children at 8 and 12 weeks
    • Most common cause of outbreaks
    • Common in
      • Hospitals, schools, care homes, cruise ships, prisons
    • Diagnosis by PCR
  • Adenovirus
69
Q

In what season is viral diarrhoea most common?

A

Winter

70
Q

How is viral diarrhoea diagnosed?

A

Diagnosis by antigen detection in stool

infection (15 decks)

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