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Yr 3 Infection > Infectious diarrhoea > Flashcards

Infectious diarrhoea Flashcards

1
Q

Define diarrhoea

A

subjective description of frequent stools predominantly made up of fluid

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2
Q

Define Gastro-enteritis

A

3 or more loose stools per day with accompanying features (objective)

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3
Q

Define dysentery

A

obvious large bowel inflammation, bloody stools

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4
Q

How many types of stool are described in the Bristol stool chart?

A

7

type 1 - separate hard lumps
type 2 - lumpy and sausage shaped
type 3 - sausage but with cracks on surface
type 4 - smooth sausage
type 5 - soft blobs
type 6 - fluffy pieces, mushy stool
type 7 - watery, entirely liquid
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5
Q

Describe the epidemiology of Gastro-enteritis (how people can acquire it)

A

Contamination of foodstuffs (eg chicken and campylobacter)

Poor storage of produce (eg bacterial proliferation at room temp)

Travel-related infections (eg salmonella)

Person to person spread (eg norovirus)

Viruses are commonest cause and campylobacter is commonest bacterial pathogen

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6
Q

some trends in food poisoning?

A

Campylobacter - most common FOODBORNE pathogen

Salmonella - causes most HOSPITAL ADMISSIONS

Poultry meat linked to most causes of food poisoning

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7
Q

Defences against enteric infections

A

Hygiene

Stomach acidity (affected by antacids and infection)

Normal flora (affected by C. Diff diarrhoea)

Immunity (affected by HIV - salmonella)

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8
Q

Clinical features of diarrhoeal illness?

A

Non-inflammatory/secretory (eg cholera)

Inflammatory (eg shigella dysentery)

Mixed picture (eg C. diff)

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9
Q

features of non-inflammatory diarrhoeal illness?

A

secretory toxin mediated

  • cholera: increases cAMP levels and Cl secretion, leading to water and sodium to also be secreted
  • enterotoxigenic E. coli (travellers diarrhoea)

frequent watery stools with little abdo pain

rehydration mainstay of therapy

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10
Q

features of inflammatory diarrhoeal illness?

A

inflammatory toxin damage and mucosal (pain and fever)

bacterial infection/amoebic dysentery

antimicrobials may be appropiate but rehydration alone insufficient

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11
Q

what parts of the presenting complaint may be particularly relevant in assessing the patient?

A
  • symptoms and their duration (over 2wks unlikely to be infective gastro-enteritis)
  • Risks of food poisoning (dietary, contact, family history)
  • Assess hydration (postural BP, skin turgor, pulse)
  • features of inflammation: SIRS (fever, raised WCC)
  • child features (sunken eyes+cheeks/decreased skin turgor/few or no tears when crying/dry mouth+tongue/sunken fontanelle)
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12
Q

what are the implications of fluid and electrolyte losses (more serious with secretory diarrhoea)

A
  • 1 to 7L fluid per day lost containing 80-100mmol Na
  • Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
  • Hypokalaemia due to K loss in stool
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13
Q

what general investigations would you carry out on a patient presenting with diarrhoea?

A
  • stool culture
  • blood culture
  • renal function
  • blood count - neutrophilia, haemolysis
  • abdominal x-ray if abdomen distended and tender
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14
Q

differential diagnosis of a patient with diarrhoea?

A
  • IBD
  • Spurious diarrhoea (secondary to constipation)
  • Carcinoma
  • diarrhoea and fever can occur with sepsis outside the gut (patient may have lack of abdo pain and tenderness which goes against gastroenteritis. Also likely to be no blood or mucus in stools)
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15
Q

treatment of gastro-enteritis?

A

Rehydration with

  • oral rehydration with salt/sugar solution (
  • iv saline

nb : note that the solution is given orally, must be given with sugar and amino acids as the uptake mechanisms are coupled with these

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16
Q

Describe key features of campylobacter gastroenteritis?

A
  • Up to 7 days incubation so dietary history may be unreliable
  • Stools negative within 6 weeks
  • abdominal pain can be severe, rarely invasive
  • post infection sequelae (GBS, reactive arthritis)
17
Q

Discuss bacterial culture of campylobacter?

A
  • commonest cause of bacterial food poisoning in UK
  • C. jejuni/c. coli
  • chickens, contaminated milk, puppies
  • isolated cases not outbreaks
18
Q

Discuss salmonella gastroenteritis and the routine bacterial culture for it?

A
  • symptom onset usually within 2 days of exposure, diarrhoea lasts <10d
  • 20% patients still have positive stools at 20/52 (associated with gallstones)
  • screened put as lactose non-fermenters then antigen and biochemical tests
  • genetically most are serotypes of same species (salmonella enterica)
19
Q

What common salmonella isolates cause:

  • gastroenteritis
  • enteric fever
A
  • Salmonella enteridis and typhimurium

- Salmonella typhi and paratyphi

20
Q

What bacteria is associated with the following:

  • infection from contaminated meat or person-to-person spread
  • characteristic frequent bloody stools
  • verocyto-toxin production by the bacteria in the gut, the toxin then gets into blood
  • toxin can cause Haemolytic-uraemic syndrome (HUS)
A

E.coli O157 infection

21
Q

Describe the patho-physiology of HUS and then classic signs and symptoms, and treatment?

A

patho-physiology

  • toxin binds to globotriaosylceramide
  • platelet activation stimulated
  • micro-angiopathy results
  • attach to endothelial, glomerular, tubule and mesangial cells

signs and symptoms

  • renal failure
  • haemolytic anaemia
  • thrombocytopenia

treatment
-supportive (no antibiotics)

22
Q

name some other bacteria associated with food poisoning outbreaks and what they are associated with?

A

> Shigella (4 species) - outbreaks of shigella sonnei in nurseries
enteropathogenic/enterotoxic(travellers diarrhoea)/enteroinvasive E.coli HOWEVER only O157 is easily diagnosed
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (toxin)

23
Q

When should antibiotics be given in gastroenteritis (and when shouldnt you give antibiotics)?

A

indicated

  • immunocompromised
  • severe sepsis or invasive infection
  • valvular heart disease
  • chronic illness
  • diabetes

contraindicated
-healthy patient with non-invasive infection

24
Q

Discuss the severity and the toxins produced in C. Diff infection?

A

Severity ranges from mild diarrhoea to severe colitis

Enterotoxin (A) and cytotoxin (B) which is inflammatory

25
Q

treatment of C. diff infection

A

-Stop precipitating antibiotic if possible
-metronidazole (if no severity markers)
-oral vancomycin (if 2 or more severity markers)
Fidaxomicin (new and expensive)
-stool transplants
surgery may be required

26
Q

Discuss prevention of CDI?

A
  • Avoid 4C’s - cephalosporins, co-amoxiclav, clindamycin and clarithromycin
  • Antimicrobial Management Team and local antibiotic policy
  • Isolate symptomatic patients
  • Wash hands between patients
27
Q

How is parasitology (usually protozoa and helminths)diagnosed

A

Microscopy

28
Q

What are the main UK parasites?

A

Giardia Lamblia

  • contaminated water. Diarrhoea, malabsorption and failure to thrive
  • distal duodenal biopsy to diagnose. Cysts seen on stool biopsy
  • treat with metronidazole

Cryptosporidium parvum

  • contaminated water, first recognised in AIDS
  • cysts seen on microscopy
  • no treatment
29
Q

Discuss Entamoeba histolytica (example of imported parasite)

A
  • amoebic dysentery
  • vegetative form in symptomatic patient (hot stool)
  • cysts seen in asymptomatic patient
  • amoebic liver abscess may be long term complication (anchovy pus)
  • treat with metronidazole
30
Q

What virus is known to cause diarrhoea in children under 5 yrs?

A

rotavirus

31
Q

how is viral diarrhoea (common in winter) diagnosed

A

antigen detection

32
Q

Discuss Norovirus:

  • does it cause outbreaks
  • diagnosis
  • protocol for management
A
  • tends to cause outbreaks in hospitals, cruise ships. Very infectious
  • PCR to diagnose
  • strict infection control measures needed. Quarantine area etc

Yr 3 Infection (12 decks)

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