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Gastrointestinal > Gastrointestinal Infections > Flashcards

Gastrointestinal Infections Flashcards

1
Q

What toxins can affect the GI tract?

A
  • Chemical
  • Bacteria
  • Viruses
  • Protozoa
  • Roundworms (nematodes)
  • Tapeworm (cestodes)
  • Flukes (tremtodes)
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2
Q

What defences does the GI system have against toxins?

A
  • sight, smell, memory
  • saliva: antibacterial enzymes
  • gastric acid
  • commensal bacteria
  • colonic mucous
  • bile in duodenum
  • anaerobic environment: small bowel + colon
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3
Q

Benefits of gut micro biome

A
  • outcompete harmful bacteria for nutrients
  • produces antimicrobial substances
  • helps develop newborn immune system
  • produce certain nutrients e.g. vitamin K
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4
Q

What do bacteria in colon produce?

A

Short chain fatty acids
e.g. acetate, propionate, butyrate

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5
Q

Function of the SCFAs produced by the bacteria in colon

A
  • Butyrate: energy source of coloncytes + helps regulate gut environment
  • Acetate: helps reduce satiety
  • propionate: reduces serum cholesterol

CHECK may not be right

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6
Q

What health conditions can decrease the diversity of the gut microbiome?

A

Obesity
Inflammatory bowel disease

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7
Q

What is faecal microbiota transplant?

A

Therapeutic procedure in which you transfer healthy donor fences into GI tract of another to restore a balanced gut microbiome.

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8
Q

Route of administration in faecal microbiota transplant

A
  • nasoduodenal tubes
  • upper GI endoscopy
  • colonoscopy
  • caecum >distributed throughout length of colon
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9
Q

What condition has been treated with faecal microbiota transplant effectively?

A

Clostridioides difficile infection

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10
Q

What is the criteria for selecting donors for faecal microbiota transplantation?

A
  • 10-25 year olds
  • not used antibiotics, laxatives or diet pills in last 3 months
  • have no GI disease
  • screen for hepatitis, HIV, inflammatory markers
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11
Q

What is dysbiosis?

A

Imbalanced gut microbiome

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12
Q

How can different diet choices affect gut microbiota?

A
  • high fibre: increases health
  • gluten free diet in those without coeliac disease: lowers number of key species
  • sweeteners: disrupt diversity
  • prebiotics: food for microbiota (good)
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13
Q

Name bacterial infections of the gut + their gram stain

A

gram negative bacilli:
- salmonella
- campylobacter
- shigella
- enterotoxigenic E. coli

gram positive
- Clostridioides difficile

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14
Q

Gram stain of salmonella bacteria

A

Gram negative bacilli

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15
Q

Symptoms of salmonella

A
  • Nausea
  • Vomiting
  • Non bloody diarrhoea
  • Fever
  • Abdominal cramping
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16
Q

How is salmonella spread?

A

Ingesting contaminated food + water

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17
Q

Outline a salmonella infection inside the gut

A
  • salmonella endocytosed into enterocytes
  • move to submucosa > taken up by macrophages
  • macrophages transfer salmonella to reticuloendothelial system
  • multiple inside cells
  • causes lymphoid hyperplasia + hypertrophy
  • re enter gut from liver
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18
Q

Gram stain of campylobacter

A

Gram negative bacilli
S shaped

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19
Q

How is campylobacter spread?

A

Via faeco-oral route
Eating poultry

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20
Q

Treatment of salmonella

A

Self limiting in 2-3 days
Fluids

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21
Q

Symptoms of campylobacter infection

A
  • fever
  • abdominal cramping
  • profuse diarrhoea (can be bloody)
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22
Q

Treatment of campylobacter infection

A
  • Self limiting (few days - weeks)
  • Fluid/electrolyte replacement
  • antibiotics if bloody diarrhoea
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23
Q

What infection is associated with eating poultry?

A

Campylobacter
(Salmonella)

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24
Q

Why do you get profuse diarrhoea in campylobacter infection?

A

Releases a cytotoxin
(Similar to cholera)

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25
Q

What does a shigella infection cause?

A

Shigellosis

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26
Q

Gram stain of shigella

A

Gram negative bacilli

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27
Q

How is shigella spread?

A

From infected stools
Person to person
Often spread between family members

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28
Q

Symptoms of shigella infection

A

Bloody diarrhoea with mucous
Abdominal cramping

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29
Q

Outline a shigella infection in the gut

A
  • endocytosed into large intestinal + rectal cells
  • break out from endocytosis vesicle
  • multiple inside cell where they are protected from macrophages
  • mucosal abscess forms as cell dies
  • causes blood diarrhoea with mucous + abdominal cramping
  • shigella invade neighbouring cells
30
Q

Who is shigella infection common in?

A

Young children
<5

31
Q

Treatment of shigella infection

A

Self limiting
Resolves in a week

32
Q

Describe enterotoxigenic E. coli

A
  • Commensal of colon but can be a pathogen
  • Gram negative bacilli
  • Has flagellum
33
Q

What is the common cause of travellers diarrhoea?

A

Enterotoxigenic E. coli

34
Q

Outline enterotoxigenic E. coli infection

A
  • ETEC adheres to enterocytes in small intestine
  • enterotoxin produced
  • causes hypersecretion of Cl- ions
  • H2O follows
  • watery diarrhoea
35
Q

What are the gram negative bacilli which can infection the GI tract?
List from shortest to longest duration

A

shortest
ETEC
Salmonella
Shieglla
Campylobacter
longest

36
Q

What is haemolytic uraemic syndrome?

A

Triad of:
- anaemia
- acute kidney disease
- thrombocytopenia

37
Q

Describe Clostridioides difficle

A

Gram positive bacilli
Anaerobic
Spore forming

38
Q

What is a major precipitating factor for Clostridioides difficle?

A

Broad spectrum antibiotics
Disrupts normal gut microbiota

39
Q

What toxins does C difficle release?

A
  • Toxin A: enterotoxin > excessive secretion > diarrhoea + inflammation
  • Toxin B: cytotoxin > kills coloncytes
40
Q

Symptoms of Clostridioides difficile

A

Mainly asymptomatic
Diarrhoea (rarely bloody)
Abdominal cramping

41
Q

Severe rare complications of Clostridioides difficle infection

A

Pseudomembranous colitis
Toxic megacolon

42
Q

Treatment of Clostridioides difficle infection

A
  • remova of offending antibitoics
  • fluid resuscitation
  • probiotics (to replace microbiota)
  • metrondiazole or vancomycin
43
Q

What does pseudomembranous colitis look like on a colonoscopy?

A

Elevated yellow plaques

44
Q

What viruses can cause viral gastroenteritis?

A

Rotavirus
Norovirus

45
Q

What parasites cause parasitic gastroenteritis?

A

Cryptosporidium
Giardia lamblia
Entamoeba

46
Q

What demographic does rotavirus effect?

A

Under 5s

47
Q

Describe rotavirus

A

Double stranded RNA virus

48
Q

Symptoms of rotavirus

A
  • vomiting
  • fever
  • diarrhoea follow
49
Q

Treatment of rotavirus

A

Manage dehydration due to fluid loss

50
Q

Mechanism of rotavirus infection

A
  • increases Cl- secretion > H2O follows > diarrhoea
  • SGLT1 disruption: reduced movement of Na+/glucose into enterocyte > higher osmotic pressure in gut > H2O moves in via osmosis > diarrhoea
  • brush border dysfunction: malabsorption
51
Q

What demographic does norovirus effect?

A

Any age
(Don’t develop immunity)

52
Q

Symptoms of norovirus infection

A

Vomiting
Water diarrhoea
Fever

53
Q

Treatment of norovirus

A

Oral rehydration therapy
Lasts 1-3 days

54
Q

What is the most common cause of non bacterial gastroenteritis?

A

Norovirus

55
Q

Mechanism of infection of norovirus

A
  • brush border enzyme disruption: infects small intestine + damages microvili
  • delayed gastric emptying > vomiting
  • anion secretion > water moves into gut > diarrhoea
56
Q

Types of pathogenic Protozoa
How do they move?

A
  • Amebas: move by extending cytoplasmic projections
  • Flagellates: move by rotating whip like flagella
  • Ciliates: move by synchronous beating of cilia
  • Sporozoa: non motile adult forms
57
Q

Describe cryptosporidium

A

Protozoa - sporozoa

58
Q

How is cryptosporidium infection spread?

A

Faecal oral route
Contaminated water with an animal faeces

59
Q

Who is cryptosporidium infection common in?

A

Travellers
Campers
Areas of poor sanitation

60
Q

Symptoms of cryptosporidium infection

A

Water diarrhoea

61
Q

Treatment of cryptosporidium

A
  • Self limiting
  • Fluid replacement
  • Anti-parasitics if at risk groups e.g AIDS
62
Q

Describe gardia lamblia

A

Flagellated protozoa

63
Q

Symptoms in gardia infection

A
  • Mainly asymptomatic
  • Symptoms more common children
  • diarrhoea
  • abdominal cramping
  • last for up to 6 weeks
64
Q

Treatment of giardia

A

Fluid replacement
Antibiotics

65
Q

Describe the life cycle of giardia parasite

A
    • cyst in ingested
    • stomach acid/pancreatic enzyme release parasite from cyst
    • multiplies in small intestine
    • damages proximal small intestine
    • parasite returns to cyst stage in colon
    • cycle repeated
66
Q

Describe entamoeba histolytica

A

Amoeba protozoa

67
Q

Symptoms of entamoeba histolytica infection

A

Most asymptomatic
Bloody diarrhoea
Liver abscesses (rare)

68
Q

Treatment of entamoeba histolytica

A

Anti protozoals
metrondiazole

69
Q

Describe the infection of entamoeba histolytica

A
  • cyst ingested
  • parasite leaves cyst in colon
  • trophozoites invade mucosa > bloody diarrhoea
  • infection can spread to liver > liver abscess (rare)
  • cysts pass out in faeces > infect others
70
Q

What parasitic infection is most likely to cause persistent diarrhoea?

A

Gardia

71
Q

What bacteria can cause haemolytic thrombocytopenia ureamia?

A

Shigella
Campylobacter

Gastrointestinal (27 decks)

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