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Semester 3 - Gastrointestinal > 16. GI infections > Flashcards

16. GI infections Flashcards

1
Q

What toxins can cause GI infections?

A
  • Chemical
  • Bacteria
  • Viruses
  • Protozoa
  • Nematodes (Roundworms)
  • Cestodes (Tapeworms)
  • Trematodes (Flukes)
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2
Q

What are some of the GI defences?

A
  • Sight, smell, memory
  • Saliva (bacteriostatic secretions)
  • Gastric acid (acidic environment)
  • Small intestinal secretions (Bile)
  • Colonic mucus
  • Anaerobic environment (small bowel, colon)
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3
Q

Define microbiota of the gut.

A

Refers to the organisms within the gut environment

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4
Q

What are the Benefits of microbiome?

A
  • Harmful bacteria cannot compete for nutrients
  • Microbiome produces antimicrobial substances
  • Helps to develop newborn’s immune system
  • Produce certain nutrients (Vit K)
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5
Q

Which part of the gut is relatively sterile?

A

Proximal gut is relatively sterile environment

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6
Q

Does the amount of bacteria increase or decrease as you go more distal into GI tract?

A

increases

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7
Q

What %of faecal mass is bacteria?

A

20 %

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8
Q

describe the environment of the colon

A

anaerobic

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9
Q

What do bacteria in the colon produce?

A

SCFAs (acetate, propionate, butyrate)

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10
Q

What does Butyrate do?

A

energy source for colonocytes, helps regulate gut environment

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11
Q

What does acetate do?

A

involved in cholesterol metabolism

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12
Q

What does propionate do?

A
  • helps regulate satiety
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13
Q

What is the general affect of health on the microbiome?

A
  • Obesity- seems to be less diverse population of bacteria
  • Inflammatory bowel disease- less diversity
  • Microbiome composition affects response to chemotherapy
  • Microbiome composition affects insulin response to food
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14
Q

What is Faecal microbiota transplant (FMT)?

A

Faecal transfer from healthy donors to the sick in order to treat disease

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15
Q

What are the routes of administration of FMT?

A

• NG/duodenal tubes (unappealing for most patients) - Can be done under anaesthetic
• Upper GI endoscopy
• Colonoscopy
• Transplant can be put in Caecum (allowed to move throughout colon)
- Distributed throughout length of colon

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16
Q

Who are the donors for FMT?

A

• 10-25 year olds
• Donors do not use (in past 3 months)
- Antibiotics
- Laxatives
- Diet pills
• Do not have GI disease
• Completely screened (inflammatory markers, Hepatitis, HIV)
• Fresh stool to transplantation or storage (1 hour!)
• Stool is centrifuged, filtered and diluted

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17
Q

What questions should be asked about history of diarrhoea?

A

onset, duration, frequency, consistency (Bristol Stool Chart), mucous/blood

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18
Q

What important parts of history should you ask about?

A
  • History of presenting complaint (diarrhoea, vomiting, pain etc)
  • Past medical history
  • Travel history (very important)
  • Drug history
  • Social history
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19
Q

What questions should be asked about history of vomiting?

A

onset, frequency

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20
Q

What questions should be asked about history of pain?

A

site, radiation, intermittent/continuous (SQITARS)

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21
Q

What important past medical history should you be aware of in a patients with suspected GI infection?

A
  • Immunodeficiency/immunocompromised state

* Other GI conditions

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22
Q

Why is social history important?

A

Important to inquire about occupation

  • if infection is infectious and patient works in area with lots of people, risk of spreading
  • patient should not go back to work until infection has settled
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23
Q

What type of drugs are important to inquire about?

A
  • Recent antibiotics
  • Proton pump inhibitors
  • Laxatives
  • Immunosuppressant medications
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24
Q

What questions are important to ask in travel history?

A
  • Where, when, how long
  • Activities
  • Food and drink
  • Animal contact
  • Travel companions & household contacts
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25
Q

What are the different investigations that can be done on a stool sample?

A
  • stool culture
  • enzyme immunoassay
  • PCR
  • Microscopy
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26
Q

Which organisms are tested for via stool cultures?

A
  • E. Coli 0156
  • Salmonella
  • Shigella
  • Campylobacter
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27
Q

Which organisms are tested for via enzyme immunoassay?

A
  • Cryptosporidium
  • Giardia
  • Clostridioides difficile
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28
Q

Which organisms are tested for via PCR?

A
  • Clostridioides
  • Entamoeba histolytica
  • Norovirus, rotavirus
  • Other bacterial
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29
Q

Which organisms are tested for via Microscopy?

A

Ova, cysts and parasites

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30
Q

Which organisms typically cause watery diarrhoea?

A
  • Norovirus, rotavirus
  • Clostridioides difficile
  • Enterotoxigenic E. coli
  • Giardia lamblia
  • Cryptosporidium parvum
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31
Q

Which organisms typically cause inflammatory diarrhoea?

A
  • Non-typhoidal salmonella
  • Campylobacter
  • Clostridioides difficile
  • Shigella
  • E. coli O157
  • Entamoeba histolytica
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32
Q

Which gram negative rods can cause bacterial infection of the gut?

A
  • Salmonella
  • Campylobacter
  • Shigella
  • Enterotoxigenic E-coli
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33
Q

Which gram positive rods can cause bacterial infection of the gut?

A

Clostridium difficile

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34
Q

What are the symptoms of gasteroenteritis caused by salmonella?

A

Nausea, vomiting and diarrhoea (mostly non-bloody), fever, abdominal cramping

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35
Q

How is salmonella spread?

A

Spread by ingesting food and water contaminated by salmonella bacteria (symptoms develop 48 hours later)

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36
Q

How is gasteroenteritis due to salmonella treated?

A

In healthy individuals this is self limiting (2-3 days)

- fluid resuscitation if needd

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37
Q

Describe the pathophysiology of the invasion of salmonella

A
  • Salmonella gain access to enterocytes (endocytosis)
  • (rare) Move to submucosa where encounter macrophages
  • Macrophages transfer salmonella to reticuloendothelial system where they multiply inside cells
  • Causing lymphoid hyperplasia
  • Re-enter gut from the liver - possible liver and gallbladder infection
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38
Q

describe the campylobacter bacteria

A
  • Spiral or ‘s’ shaped organism

* Mainly microaerophilic (do not ferment carbs)

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39
Q

What are the possible complications of salmonella and who is at a greater risk of developing them?

A
  • bacteraemia
  • endovascular infections,
  • abscesses
  • osteomyelitis & septic arthritis (more likely in sickle cell disease)
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40
Q

Where is Camplyobacter found?

A

Found in GI tract of animals especially poultry.

- raw foods cause infection

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41
Q

What is the incubation period and transmission route of Campylobacter?

A
  • Spread to humans via faeco-oral route
  • Needs to multiply within host before symptoms appear (food infection- not food poisoning)
  • Longer incubation period (1-7 days)
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42
Q

What are the general features of gasteroenteritis due to Campylobacter?

A

• Fever, abdominal cramping, profuse diarrhoea (can be bloody)

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43
Q

If diarrhoea is bloody in campylobacter, what does it suggest?

A

invasion infection of colon

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44
Q

How long does gasteroenteritis due to Campylobacter last?

A

Can lasts days to weeks (generally self limiting)

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45
Q

What is released by campylobacter that causes profuse diarrhoea?

A

• Releases a cytotoxin (similar to cholera)

46
Q

What is the treatment for Campylobacter?

A
  • Fluid/electrolyte replacement

* Consider antibiotics if bloody diarrhoea

47
Q

What does the bacteria shigella cause and who does it commonly affect?

A

Causes shigellosis which is a dysentery commonly affecting young children < 5 years

48
Q

What is the transmission route of shigella?

A

• Transmission: faeco-oral, food and water. Person-to-person transmission can occur due to low infective dose

49
Q

What are the symptoms of gasteroenteritis due to shigella and what are the reasons behind them?

A
  • Invades large intestine colonocytes, multiplies in cells and invades neighbouring cells
  • This kills colonocytes and forms abscesses in the mucosa
  • Bloody diarrhoea with mucus and abdominal cramping
50
Q

What is the treatment of shigella?

A

Usually resolves in a week

51
Q

Describe Enterotoxigenic E-coli

A

• Commensal of the colon but can also be a pathogen

52
Q

How is Enterotoxigenic E-coli spread?

A

Spread by faecal oral route or by contaminated food and water

53
Q

What is enterotoxigenic E-coli a common cause of?

A

travellers diarrhoea

54
Q

What is the pathophysiology of gasteroenteritis due to enterotoxigenic E-coli?

A
  • colonise and adhere to enterocytes (produces enterotoxins)
  • These cause the hypersecretion of chloride ions from enterocyte to lumen
  • Water leaves cells into the gut lumen
55
Q

How are gram negative bacteria that cause gasteroenteritis spread?

A

oral route from different sources- faecal, food, water

56
Q

Which of the gram negative bacteria causing gasteroenteritis cause dairrhoea?

A

Diarrhoea (all)
• Potentially bloody (Shigella, campylobacter)
• Watery (ETEC, salmonella)

57
Q

Which of the gram negative bacteria causing gasteroenteritis release toxins?

A

All

58
Q

Which of the gram negative bacteria causing gasteroenteritis potentially cause haemolytic uraemic syndrome??

A

Shigella, campylobacter)

59
Q

What is haemolytic uraemic syndrome?

A

A triad of anaemia, thrombocytopaenia and AKI

60
Q

To which of the gram negative rod infections are antibiotic prescribed?

A

Antibiotics are carefully prescribed for serious cases (resistance becoming a problem)

61
Q

order the gram negative rod bacteria into shortest to longest duration

A

ETEC, salmonella (days), Shigella (week), campylobacter (weeks)

62
Q

Which one of these gram negative rods is most likely to cause bloody diarrhoea?

A

shigella

63
Q

describe clostridium difficile

A

• Gram positive , anaerobic, spore forming bacillus

64
Q

how is clostrdium difficile spread?

A

Minor component of the GI tract but can be transferred via faecal-oral route

65
Q

why is clostridium difficile gasteroenteritis spread easily?

A

Spores are very difficult to get rid of from an environment (like a hospital)

66
Q

What is the major precipitating factor in gastroenteritis caused by C difficile?

A

antibiotics!

• Following antibiotic therapy C-difficile can colonise gut and release toxins

67
Q

what are the actions of the toxins released by c difficile?

A
  • Toxins A & B
  • A- enterotoxin that results in excessive secretion of water(+ inflammation)
  • B- Cytotoxin - kills colonocyte
68
Q

How does gastroenteritis caused by C difficile present?

A
  • Asymptomatic (most people)
  • Varying degrees of diarrhoea (mild to terrible, rarely bloody)
  • Abdominal cramping
69
Q

Which antibiotics particularly lead to c difficile infection?

A

Most antibiotics can precipitate C- difficile proliferation (especially broad spectrum)

70
Q

What are some of the complications of c difficile gastroenteritis?

A

In a few cases (<5%)
• Pseudomembranous colitis
• Toxic megacolon (worst case scenario) - Surgery

71
Q

What is Pseudomembranous colitis?

A
  • Inflammatory condition

* Elevated yellow plaques join to form a pseudomembrane

72
Q

What is the Treatment of C. difficile infection?

A
  • Remove offending antibiotic
  • Fluid resuscitation
  • Metronidazole/Vancomycin
  • Probiotics
73
Q

Which virus is a very common cause for gastroenteritis in the under 5s?

A

Rotavirus

74
Q

What type of virus is the rotavirus?

A

Double stranded RNA virus

75
Q

How is rotavirus spread?

A

Spread faecal-oral route (only very small dose required)

76
Q

Are adults affected by rotavirus and why?

A

Adults rarely affected (immunity lasts into adulthood)

77
Q

What are the symptoms of rotavirus gastroenteritis?

A
  • Vomiting with a fever are first symptoms

* Diarrhoea follows (lasting up to a week)

78
Q

What causes diarrhoea in rotavirus gastroenteritis??

A
  • Chloride secretion
  • SGLT1 disruption
  • Reduced brush border enzyme function
79
Q

Describe how chloride secretion can lead to diarrhoea in rotavirus gastroenteritis?

A
  • Creates gradient for the movement of Na into lumen
  • Water moves by osmosis following Na
  • Diarrhoea
80
Q

Describe how SGLT1 disruption can lead to diarrhoea in rotavirus gastroenteritis?

A
  • Reduced movement of Na/glucose into enterocyte
  • Higher osmotic load in gut
  • Water moves by osmosis
81
Q

Describe how Brush border dysfunction can lead to diarrhoea in rotavirus gastroenteritis?

A

malabsorption, increased osmotic pressure in lumone, water moves by osmosis into lumen

82
Q

What is the Most common cause of non bacterial gastroenteritis in the world?

A

Norovirus

83
Q

What age does norovirus gastroenteritis affect?

A

• Can affect any age as there are huge number of strains (don’t develop immunity)

84
Q

Why is norovirus highly contagious?

A
  • Only requires small dose so highly contagious

* Virus resistant to cleansing

85
Q

What is the incubation period for norovirus and how long do symptoms last?

A

Incubation is 1-2 days and symptoms last 1-3 days

86
Q

Which part of the GI tract does norovirus affect?

A

Infects the small intestine and damages microvilli (brush border enzymes disruption)

87
Q

What are the symptoms of norovirus gastroenteritis and explain them?

A
  • Symptoms include vomiting, watery diarrhoea, fever
  • Anion secretion, so movement of water into gut lumen
  • Vomiting is due to delayed gastric emptying - pressure in stomach increases
88
Q

what is the treatment for norovirus gastroenteritis?

A

Treatment is oral rehydration therapy

89
Q

What are the main pathogens of parasitic gastroenteritis and what are their classifications?

A 
Protozoa that infect the intestinal tract
• Cryptosporidium
--> Sporozoan - non motile
• Giardia lamblia
--> Flagellate - motile
• Entamoeba
--> Amoeba - motile
90
Q

How is Cryptosporidium spread?

A

Transmitted by the faecal-oral route but can also be survive and spread via bodies of water (infected by animal faeces)

91
Q

How does Cryptosporidium cause gastroenteritis?

A

Disease is caused by the ingestion of an oocyst (a cyst containing the parasite)
• This reproduces inside the epithelial cells of the distal small intestine
• Oocysts are excreted in faeces to continue cycle

92
Q

What are the symptoms of gastroenteritis due to Cryptosporidium?

A

Produces watery diarrhoea that is normally self limiting
• Malabsorption (brush border enzymes affected)
• Chloride secretion

93
Q

What is the treatment for gastroenteritis due to Cryptosporidium?

A
  • Treatment is supportive (fluids)
  • Occasionally anti-parasitic treatment in at risk groups
  • AIDS- can produce severe symptoms
94
Q

Who are giardia gastroenteritis more common in?

A

in children

95
Q

How id giardia spread?

A

Spread via faecal-oral route with water supplies often affected (in developing countries)

96
Q

What are the symptoms of giardia gastroenteritis?

A 
• Most infections are asymptomatic 
• If symptomatic (appear after 10+ days incubation period)
• Diarrhoea
• Abdominal cramping
• Can last up to 6 weeks
Common cause of persistent diarrhoea
97
Q

Describe the two stages of the life cycle of giardia

A
  1. Cyst is ingested
    • Stomach acid/ pancreatic enzymes release parasite from cyst
    • which then multiplies in small intestine- incubation 1-2 weeks
    • Damages proximal small intestine causing symptoms (diarrhoea)
    • Villous atrophy occurs
  2. Parasite then goes back into cyst stage in colon
    • Excreted to repeat the cycle
98
Q

What is the treatment for giardia gastroenteritis?

A

• Antibiotics and fluid rehydration therapy

99
Q

What is common post giadia infection?

A

lactase deficiency is common

• Lactose intolerance

100
Q

Where is Entamoeba histolytica gastroenteritis common?

A

Higher prevalence in developing countries

Affects:
• People who have travelled to tropical places that have poor sanitary conditions
• People who live in institutions that have poor sanitary conditions
• Men who have sex with men

101
Q

What are the symptoms of entamoeba histolytica gastroenteritis?

A
  • Most cases are asymptomatic (80%)
  • If symptomatic:
  • Diarrhoea
  • Liver abscesses (rare)
102
Q

How is entamoeba histolytica spread?

A

Transmitted by faecal-oral route (from contaminated food or water)

103
Q

Describe what happens in entamoeba histolytica gastroenteritis

A
  • Infection follows the ingestion of cysts
  • Excystation occurs in colon where trophozoites invade mucosa
  • Bloody diarrhoea and inflammatory changes occur (similar to IBD)
  • Infection can also spread to liver (abscesses form)
  • Cysts then pass out with faeces- infect others
104
Q

What is the treatment for entamoeba histolytica gastroenteritis?

A
  • Anti-protozoals/metronidazole

* Severe colitis/toxic megacolon may require surgery

105
Q

What is travellers diarrhoea?

A

Diarrhoea is the most common symptom of travel related illnesses
• Defined as passing 3 or more loose/watery stools
• +/- fever, abdominal pain

106
Q

What is the most common cause of traveller’s diarrhoea?

A

• Enterotoxic Escherichia coli (ETEC) is the most common cause of acute travellers’ diarrhoea globally

107
Q

What factor reduces the likelihood of a bacterial cause of travellers diarrhoea?

A

Greater than 14 days of symptoms makes it less likely to be bacterial in cause

108
Q

How is travellers diarrhoea treated?

A

Mild/moderate (less than 6 stools/24 hrs)
• Hydration (oral rehydration solutions/ safe water)
• Antidiarrhoeal agents

Severe (more than 6 stools/24 hrs)
• IV fluids (potentially)
• Antibiotics (if appropriate)

109
Q

What increases the risk of developing travellers diarrhoea?

A
  • Place you are visiting (south and east asia, central America, west and north Africa)
  • Dietary exposure (backpacking)
  • Less than 6 years, PPIs, Blood group O (shigellosis, cholera
110
Q

Who are given antibiotics when presenting with traveller’s diarrhoea?

A
  • Antibiotics are only recommended for vulnerable patients (immunosuppressed)
  • Halves duration of symptoms (to 1.5 days on average)

Semester 3 - Gastrointestinal (17 decks)

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