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Year 3 - Infection > Infectious diarrhoea > Flashcards

Infectious diarrhoea Flashcards

1
Q

List the bacteria that are sought by routine culture of stools from patients with diarrhoea in the UK and outline their epidemiology (6)

List other bacteria (4) that cause diarrhoea, indicate the availability of routine tests for them

A

Routine:
Salmonella (S. sonnei, S.flexneri, S.boydii, S. dysenteriae)
campylobacter,
E. coli O157,
shigella,
clostridium (C. perfringens, C. difficile)
cryptosporidium

Cholera
Other forms of E. coli (enterotoxigenic E. coli)
Staph aureus (toxin)
Bacillus cereus (re-fried rice)

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2
Q

List the parasites commonly detected in stool specimens in the UK by microscopy

A

Giardia duodenalis (aka G. lamblia/G. instestinalis)
Cryptosporidium parvum
Entamoeba histolytica

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3
Q

List the viruses that commonly cause diarrhoea (3)

A

Rotavirus,
Norovirus,
Adenovirus (serotypes 40/41)

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4
Q

Define

  • food-poisoning
  • gastro-enteritis
  • dysentery
  • colitis.
A

Gastro-enterits
-3+ loose stools in 24hrs plus at least one of fever, vomiting, pain, blood/mucus stools

Dysentery
-large intestine inflammation, bloody stools

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5
Q

Commonest pathogenic cause of gastro-enteritis

A

Virus

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6
Q

Commonest bacterial cause of gastro-enteritis

A

Campylobacter

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7
Q

Host’s natural defences against enteric infections (6)

A 
Age
HYGIENE
Stomach acidity
Gut motility
Normal gut flora
Gut Immunity
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8
Q

Mechanisms of diarrhoea

A

toxin mediated, invasion, attachment

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9
Q

2 types of diarrhoea

A

Non-inflammatory/secretory:

  • Toxin-mediated usually
  • Watery stools, rapid dehydration, relatively little abdo pain
  • Rehydration mainstay of treatment

Inflammatory:

  • Bacterial infection usually
  • Abdo pain, bloody stools, sytemic upset
  • Rehydration and (sometimes) antimicrobials required
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10
Q

An example of non-inflammatory/secretory diarrhoea

A

Cholera

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11
Q

An example of inflammatory diarrhoea

A

Shigella

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12
Q

Mechanism of cholera in causing non-inflammatory diarrhoea

A

Cholera is TOXIN-MEDIATED

  • toxin produced stimulates adenylate cyclase which subsequently increases cAMP levels results in loss of Cl- from intestinal epithelial cells along with Na+ and K+
  • so creates big osmotic pressure that drags water out from gut cells INTO LUMEN
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13
Q

Mechanism of inflammatory diarrhoea, e.g. shigella

A

Bacterial infection causes mucosal destruction by inducing pro-inflammatory cytokine release; these cytokines attract immune cells to destruct the epithelium lining the gut mucosa

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14
Q

Taking the history of someone with diarrhoea

  • what to ask about symptoms (4)
  • risks (6)
A

duration of diarrhoea, frequency and consistency of stool, other symptoms

Risks - food, occupation, travel, antimicrobials, contacts, institution (i.e. hospital, school)

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15
Q

If diarrhoea symptom duration >2 weeks then diagnosis unlikely to be…

A

infective gastro-enteritis

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16
Q

Examination of hydration status in diarrhoeal patient

-what to examine

A

Pulse,
Postural BP
skin turgor (not great as you lose this as you age anyway)

17
Q

Signs of gastro-enteritis in infant/child

A 
Decreased skin turgor
Sunken eyes and cheeks
Sunken fontanelle
Dry mouth/mucous membranes
Sunken abdomen
18
Q

General investigations of gastro-enteritis

A 
Stool and blood culture, 
renal function, 
Full blood count - looking for neutrOphilia, haemolysis (indicates E. coli O157)
sigmoidoscopy, 
Abdo X-Ray, 
serology
19
Q

Differential diagnosis of gastro-enteritis

A

IBD

Sepsis - diarrhoea as response to sepsis

20
Q

General treatment of gastro-enteritis

A

Rehydration therapy - salt/glucose solution or IV saline
Fasting?
Anitbiotics?
Treat complications

21
Q

Occasional causes of food poisoning outbreaks

A 
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (undercooked meat/cooked food left out - toxin accumulates in spore formation)
22
Q

Antibiotics only indicated in gastro-enteritis if

A

immunocompromised
severe sepsis or invasive infection (i.e. not localised to gut anymore)
chronic illness e.g. malignancy

23
Q

The 4 ‘C’ antibiotics that induce C. diff diarrhoea

A

cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin

24
Q

Ways of preventing C. diff diarrhoea

A
  • Reduce broad spectrum antibiotic use
  • Avoid 4 Cs
  • Wash hands with SOAP + WATER (spores are resistant to alcohol gel)
  • Clean environment on discharge

Year 3 - Infection (12 decks)

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