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Infection > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

Definitions of diarrhoea, gastroenteritis, dysentery.

A

Diarrhoea - fluidity, frequency
Gastroenteritis - three or more loose stools a day
Dysentery - large bowel inflammation, bloody stools

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2
Q

Non-inflammatory/secretory diarrhoea

A
  • secretory toxin-mediated
    - cholera - increases cAMP levels and Cl secretion
    - enterotoxigenic E. coli (travellers’ diarrhoea)
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3
Q

Presentation of non-inflammatory diarrhoea

A

Frequent watery stools with little abdominal pain

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4
Q

Treatment of non-inflammatory/secretory diarrhoea

A

Rehydration mainstay of therapy

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5
Q

Inflammatory diarrhoea

A
  • inflammatory toxin damage and mucosal destruction

- bacterial infection / amoebic dysentery

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6
Q

Inflammatory diarrhoea presentation

A

Pain and fever

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7
Q

Treatment of inflammatory diarrhoea

A

Antimicrobials may be appropriate but rehydration alone is often sufficient

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8
Q

Assessing patient with diarrhoea

A 
-Symptoms and their duration
      –>2/52 unlikely to be infective gastro-enteritis
-Risk of food poisoning
      -Dietary, contact, travel history
-Assess hydration
      –postural BP, skin turgor, pulse
-Features of inflammation (SIRS)
      -fever, raised WCC
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9
Q

Fluid and electrolyte losses

A

Can be severe with secretory diarrhoea

  - 1-7 l fluid per day containing 80-100 mmol Na
  - Hyponatraemia due to sodium loss
  - Hypokalaemia due to K loss in stool
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10
Q

Investigations for patients with diarrhoea

A
  • stool culture +/- molecular or Ag testing
  • blood culture
  • Renal function
  • blood count - neutrophilia, haemolysis (E. Coli O157)
  • abdominal X-Ray/CT if abdomen distended, tender
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11
Q

Differential diagnosis of diarrhoea

A
  • Inflammatory bowel disease
  • Spurious diarrhoea -secondary to constipation
  • Carcinoma
  • Sepsis outside the gut
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12
Q

Sepsis outside the gut presentation

A

-Diarrhoea and fever
–Lack of abdo pain/tenderness goes against gastroenteritis
–No blood/mucus in stools

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13
Q

Gastroenteritis treatment

A
  • rehydration
    - oral rehydration with salt/sugar solution
    - IV saline
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14
Q

Campylobacter gastroenteritis

A

-Campylobacter is the most common food born pathogen
-Up to 7 days incubation so dietary history may be unreliable
-Stools negative within 6 weeks
-abdominal pain can be severe
-<1% invasive
–Post-infection sequelae
-Guillain-Barre syndrome, Reactive arthritis

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15
Q

Salmonella gastroenteritis

A
  • symptom onset usually <48 hrs after exposure
  • diarrhoea usually lasts <10 days
  • post-infectious irritable bowel is common
  • prolonged carriage may be associated with gallstones
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16
Q

Salmonella gastroenteritis investigation results

A
  • <5% positive blood cultures

- 20% patients still have positive stools at 20/52

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17
Q

Commonest salmonella isolates in the UK

A
  • Salmonella enteritidis

- Salmonella typhimurium

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18
Q

E. coli O157

A
  • produces Shiga toxin
  • stays in the gut but the toxin gets into the blood
  • toxin can cause hemolytic-uraemic (HUS) syndrome
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19
Q

E. coli O157 presentation

A

frequent bloody stools

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20
Q

Hemolytic-uraemic syndrome (HUS)

A

HUS characterised by renal failure, haemolytic anaemia and thrombocytopenia

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21
Q

Hemolytic-uraemic syndrome (HUS) treatment

A

Treatment supportive – antibiotics NOT indicated

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22
Q

Indication for antibiotics in gastroenteritis

A
  • immunocompromised
  • severe sepsis or invasive infection
  • chronic illness e.g. malignancy
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23
Q

Clostridiodes difficile diarrhoea

A
  • Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics”
  • Severity ranges from mild diarrhoea to severe colitis
  • C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)
24
Q

Clostridiodes difficile diarrhoea treatment

A
  • metronidazole
  • oral vancomycin
  • Fidaxomicin (new and expensive)
  • stool transplants
  • surgery may be required
25
Q

Clostridiodes difficile infection prevention

A
  • Reduction in broad spectrum antibiotics
  • Avoid 4 Cs
  • Isolate symptomatic patients
  • Wash hands between patients (spores resist alcohol rubs)
  • Cleaning environment
26
Q

4 C’s

A
  • cephalosporins
  • co-amoxiclav
  • clindamycin
  • ciprofloxacin
27
Q

Clostridiodes difficile infection management

A
  • Stop precipitating antibiotic (if possible)
  • Oral metronidazole if no severity markers
  • Oral vancomycin if 2 or more severity markers
28
Q

Cholera

A

-a secretory diarrhoeal disease caused by the gram negative bacterium Vibrio cholera

29
Q

Cholera presentation

A

-patients present passing large quantities of rice water stools

30
Q

Cholera diagnosis

A
  • basic laboratory tests non-specific
  • culture of the organism is specific
  • rapid dipstick tests are available
31
Q

Cholera treatment

A
  • most patients will recover if the effects of the ensuing profound volume depletion are combated by oral and/or intravenous rehydration
  • antibiotics shorten duration and severity of disease, but rising rates of bacterial resistance are becoming problematic
32
Q

Shigella infection

A
  • easily spread by faecal-oral contact or by contaminated water or food
  • usually presents as mild self limiting diarrhoeal illness
  • HUS and seizures may complicate
  • different serotypes hamper development of a universal vaccine
33
Q

Rotavirus

A
  • most common viral enteropath
  • faecal-oral transmission
  • infects mature enterocytes of villous body and tip (not crypts) with cell death and lactose intolerance
34
Q

Rotavirus diagnosis

A

-antigen detection in stool

35
Q

Norovirus

A
  • very infectious -18 virus particles
  • ward closures common – staff and patients affected
  • strict infection control measures needed
36
Q

Norovirus diagnosis

A

-PCR

37
Q

Norovirus environmental association

A

-Institutional care, hospitals and care homes

39
Q

Intestinal parasites - Cryptosporidium parvum - Cryptosporidosis

A
  • outbreaks associated with contaminated drinking water supplies, fresh produce, swimming pools, children’s day care facilities and petting farms
  • disease is self limiting in immunocompetent patients
  • patients who are severely immunocompromised may suffer chronic, severe and intractable illness
40
Q

Cryptosporidiosis presentation

A
  • watery diarrhoea
  • abdominal cramps
  • loss of appetite
  • low grade fever
  • nausea and vomiting
  • > 7 days
41
Q

Cryptosporidiosis diagnosis

A

-detection of oocytes, antigens, or DNA in stool samples

42
Q

Giardia duodenalis transmission

A
  • direct contact with cattle/cats/dogs/other people

- food/water contaminated with faeces

43
Q

Giardiasis presentation

A
  • diarrhoea
  • abdominal bloating and discomfort
  • malabsorption
  • failure to thrive
44
Q

Giardiasis diagnosis

A

-detection of cysts or trophozoites in stool sample

45
Q

Giardia lambda is associated with:

A

-contaminated water supplies

46
Q

Entamoeba histolytica (causes amoebiasis) presentation

A
  • may mimic ulcerative colitis
  • diarrhoea
  • abdominal pain
  • fever
47
Q

Giardiasis treatment

A
  • metronidazole

- tinidazole

48
Q

Entamoeba histolytica (causes amoebiasis) diagnosis

A
  • detection of a Entamoeba histolytica antigen or

- DNA in stool or antibodies against the parasite in serum (invasive disease)

49
Q

Entamoeba histolytica (causes amoebiasis) complications

A
  • spread from the intestine can cause liver abscess
  • extension from liver abscess can lead to pleural and pericardial effusion
  • rarely, brain abscesses may occur
50
Q

Entamoeba histolytica (causes amoebiasis) treatment

A
  • metronidazole (or tinidazole)

- luminal agent to clear colonisation (paromomycin)

52
Q

Entamoeba histolytica is associated with:

A

-foreign travel and poor hygiene

53
Q

Use of blood cultures in infectious diarrhoea

A

Rarely helpful, but should be done in all patients to exclude invasive Campylobacter / Salmonella spp.

54
Q

Use of toxin testing in infectious diarrhoea

A

To confirm C. difficile infection

55
Q

Use of stool cultures in infectious diarrhoea

A

-to isolate bacterial pathogens e.g. Campylobacter sp., Salmonella sp., Shigella, E.coli

56
Q

Use of stool microscopy for infectious diarrhoea

A
  • best for parasitic causes
  • on stool culture requests, specify that you’re looking for ova, cysts and parasites, along with any relevant travel history
57
Q

Use of viral PCR/antigen testing for infectious diarrhoea

A
  • to confirm norovirus / rotavirus infection

Infection (15 decks)

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