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Infection > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

Define diarrhoea

A

Fluidity and frequency

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2
Q

Define gastro-enteritis

A

3+ loose stools/day & accompany features

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3
Q

Define dysentery

A

Type of GE
Large bowel inflammation
Bloody/mucusy stools
(& fever, abdo pain etc.)

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4
Q

Define chronic diarrhoea

A

Diarrhoea lasting for more than 14 days

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5
Q

What may cause GE?

A

Contamination of foodstuffs, e.g. campylobacter and chicken
Poor storage, e.g. bacterial proliferation at room temperature
Travel related infections, e.g. salmonella
Person to person spread, e.g. norovirus

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6
Q

What is the most common cause of GE?

A

Viruses

Most common bacterial cause in UK: campylobacter

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7
Q

What are our natural defences against GE?

A

Hygiene, stomach acidity, normal flora, immunity

NB - therefore antacids, and those with HIV are at greater risk of GE

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8
Q

What are two non-inflammatory diarrhoeas?

A

Cholera and enterotoxogenic E. coli (traveller’s diarrhoea)

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9
Q

Describe the mechanism by which cholera vibrio causes diarrhoea

A

Releases a toxin which is endocytosed by enterocytes Via G5, the toxin stimulates adenylyl cyclase which increases the levels of cAMP
cAMP activates the CFTR channel –> efflux of Cl –> efflux of water and other ions

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10
Q

Describe the mechanism by which enterotoxogenic E. coli causes diarrhoea

A

Toxin, via G5 stimulates adenylyl cyclase –> increased cAMP levels –> increased chloride secretion –> increased water secretion

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11
Q

Give an example of an inflammatory diarrhoea

What happens in inflammatory diarrhoea?

A

Shigella/amoebic dysentry
(which causes bloody diarrhoea, pain and fever)

Inflammatory toxin damage and mucosal destruction

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12
Q

Symptom duration >2/52 is likely to be what?

A

Unlikely to be infective GE

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13
Q

What questions do you need to ask in a history of suspected infective GE?

A

Dietary, contact, travel history

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14
Q

How could you assess a patient with diarrhoea for dehydration?

A

Postural BP, skin turgor, pulse

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15
Q

What are signs of dehydration in children?

A

Sunken fontanelle, few/no tears, dry mouth/tongue, decreased skin turgor, sunken eyes/cheek/abdomen

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16
Q

What must you also assess the patient for?

A

Features of inflammation - SIRS (fever, raised WCC)

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17
Q

What complications are associated with diarrhoea?

A

Hyponatraemia, hypokalaemia, normal anion gap metabolic acidosis, severe fluid loss

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18
Q

How do you investigate suspected infective GE?

A 
Stool culture 
Blood culture
Renal function 
FBC - neutrophilia, haemolysis
Abdo X-Ray 
Suspected parasite: microscopy (e.g. send stool with request such as parasites, cysts and ova)
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19
Q

What are potential differentials for GE?

A

IBD/IBS
Spurious diarrhoea
Carcinoma
Due to sepsis outside the gut

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20
Q

How do you manage GE?

A

Rehydration is mainstay
Salt and sugar solution if oral
IV saline

21
Q

What are the bacterial causes of diarrhoea?

A 
Campylobacter 
Salmonella
E. coli 
Shigella 
Staph aureus
Bacillus cereus
22
Q

Campylobacter GE

A

Up to 7 day incubation period
Abdo pain
Flu like predrome
Post-infection sequelae: GB syndrome, reactive arthritis

Caused by: C. jejuni, C. coli
Sources: chicken

23
Q

Salmonella GE

A

Symptom onset <48h post exposure
Diarrhoea lasts <10 days
Prolonged carriage assoc. w. gallstones
Post infectious IBS common

Caused by: s. enterica spp (s. enteritidis, a. typhidmurium)
50% from abroad

24
Q

E. coli 0157

A

Contaminated meat/person to person spread
Frequent bloody stools
Produces verocytotoxin which enters blood and may cause HUS

25
Q

What is HUS?

A

Haemolytic uraemic syndrome
Triad of: haemolytic anaemia, thrombocytopenia and AKI

Caused by toxin binding to globotriasolyceramide on glomerulus –> actives platelets –> thrombotic microangiopathy (microthrombi occlude arterioles/capillaries)

26
Q

How do you test for salmonella GE?

A

Screened as lactose non-fermenters, then antigen and biochemical tests

27
Q

How do you treat HUS?

A

Antibiotics not indicated

28
Q

Shigella

A

Outbreaks of shigella sonnei in nurseries

Causes bloody diarrhoea, ab pain and vomiting

29
Q

Bacillus cereus

A

Two patterns seen:

  • Vomiting within 6h usually due to rice
  • Diarrhoeal illness after 6h
30
Q

When are antibiotics indicated in the treatment of GE?

A 
Immunocompromised
Severe sepsis/invasive infection 
Valvular heart disease
Chronic disease
Diabetes
31
Q

Clostridium difficle

A

Recent antibiotic use (esp. 4 Cs)
Severity variable: mild diarrhoea –> severe pseudomembranous colitis (inflammation of the large bowel due to C. diff overgrowth)

C. diff produces endotoxin A and cytotoxin B

32
Q

How do you treat C. diff infection?

A
  1. stop precipitating antibiotics (clarithromycin, clindamycin, co-amoxiclav, cephalosporins)
  2. oral metronidazole (if no severity markers)
  3. oral vancomycin (if 2+ severity markers)
  4. fidamoxicin
  5. stool transplant
  6. surgery
33
Q

How can we prevent c. diff infections?

A

Reduce broad spectrum antibiotic use
Antimicrobial management team and local antibiotic policy
Isolate symptomatic patients
Wash hands b.w patients

34
Q

Giardia Lamblia

A

Contaminated water
Diarrhoea, malabsorption, failure to thrive
Non-bloody diarrhoea, that comes on gradually and can last a long time
UK parasite
Vegetative form in duodenal biopsy/string test (swallow capsule that extends string from mouth to top of duodenum, pulled back out and examined under microscopy)

Two forms of GL: dormant (cysts), trophozites (active)

35
Q

How do you treat giardia lamblia?

A

Metronidazole

36
Q

Cryptosporidium parvum

A

HIV/immunocompromised
Contaminated water/animal faeces
Cysts on microscopy
Supportive Rx

37
Q

Amoebic dysentry

A

Blood diarrhoea, lasts quite long
Vegetative form in symptomatic patient (hot stool)
Cysts in asymptomatic patient

Complications: amoebic liver abscess (which produces anchovy pus)

38
Q

How do you treat amoebic dysentery?

A

Metronidazole

39
Q

Rota virus

A

Under 5s
Common in winter
Dx: antigen detection
Vomiting, non-bloody diarrhoea

40
Q

Adenovirus

A

Certain strains can cause diarrhoea

41
Q

Norovirus

A

Winter, vomiting bud
Common cause of outbreaks (hospital, nursing homes etc.)
Dx: PCR
V. infectious - strict ICP controls req.

42
Q

Define travellers diarrhoea

A

3+ loose stools in 24h with/without 1+ of: ab cramps, fever, nausea, vomiting, blood in stools

43
Q

What is the commonest cause of traveller’s diarrhoea?

A

E. coli

44
Q

What is acute food poisoning?

A

Sudden onset N, V and diarrhoea after ingestion of a toxin

45
Q

What tends to cause acute food poisoning?

A

Staph aureus
Bacillus cereus
Clostridium perfringes

46
Q

Staph aureus diarrhoea

A

Severe vomiting

Short incubation period

47
Q

What are the incubation periods for:

a. Staph aureus, bacillus cereus
b. Salmonella, E. coli
c. Shigella, campylobacter
d. Giardiasis, Amoebiasis?

A

a. 1-6h
b. 12-48h
c. 48-72h
d. >7 days

48
Q

What organism causes giardiasis?

A

Flagellated protozoan giardia lamblia

49
Q

How is Giardia lamblia spread?

A

Faecal oral route

Infection (22 decks)

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