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ESA 3 - Gastrointestinal System > Gastrointestinal Infections > Flashcards

Gastrointestinal Infections Flashcards

1
Q

What are our GI defences against illness?

A

Sight smell memory - not go near stuff

Saliva (bacteriostatic secretions)

Gastric acid (acidic environment)

Small intestinal secretions (bile)

Colonic mucus

Anaerobic environment (small bowel, colon)

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2
Q

What are the benefits of the microbiome?

A

Harmful bacterial cannot compete for nutrients

Microbiome produces antimicrobial substances

Helps to develop newborn’s immune system

Produce certain nutrients (vitamin k)

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3
Q

What do gut bacteria produce?

A

SCFAs - acetate, propionate, butyrate

Butyrate - energy source for colonocytes, helps regulate gut environment

Acetate - Involved in cholestrol metabolism

Propionate - helps regulate satiety

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4
Q

How is the gut microbiome related to health?

A

Obese and IBD- less diverse population of bacteria.

Microbiome composition affects response to chemotherapy and insulin response to food

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5
Q

What things influence the gut microbiota?

A

High fibre diets influence the composition of it microbiota (increase in health)

Sweetners disrupt diversity of gut microbiota

Gluten free diet in people without gluten sensitivity or coeliac disease - lower numbers of key species (bad)

PPIs - increased GI infections

Antibiotics (in meat) - link to obesity as disrupt microbiota

Probiotics - live bacteria and yeasts put in food.

Prebiotics - essentially food for microbiota

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6
Q

What is FMT?

A

faecal microbiota transplant. -faecal transfer from health donors to the sick to treat a disease.

A stool is a biologically active complex mixture of living organisms with therapeutic potential.

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7
Q

Where can faeces be transplanted?

A

NG / duodenal tubes - under anaesthetic

Upper GI endoscopy

Colonoscopy

Transplant can be put in caecum (allowed to be moved throughout the colon)

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8
Q

Describe some uses of FMT

A

Diarrhoea in C. Diff infection - up to 90% resolution compared to only 30% with vancomycin

IBD - 70% resolution of symptoms and reduction / cessation of IBD medications within 6 weeks.

Crohn’s disease - Clinical remission in 50% of patients

Pseudomembranous colitis

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9
Q

Where do we get the faeces from?

A

10-25 year olds

Donors do not use:

  • Antibiotics
  • Laxitives
  • Diet pills

Do not have GI diseases

Completelyscreened (inflammatory markers, hepatitis, HIV)

Fresh stool to transplantation or storage (1 hour!) - stool is centrifuged, filtered and diluted.

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10
Q

Describe the symptoms of salmonella

A

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

It is self limiting

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11
Q

How is salmonella spread?

A

Ingesting contaminated food / water (symptoms develop 48hours later).

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12
Q

How does salmonella infect (inside gut)?

A

Salmonella gains access to enterocytes via endocytosis.

Moves to submucosa where encounter macrophages

Macrophages transfer salmonella to reticuloendothelial system where they multiply inside cells.

Causing lymphoid hyperplasia.

Re-enter gut form liver.

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13
Q

What is Campylobacter?

A

It is a spiral or S shaped gram negative rod that causes gastroenteritis.

It is mainly microaerophilic (does not ferment carbs)

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14
Q

Describe a typical campylobacter infection

A

Spread faecal-orally

Needs to multiply within host before symptoms appear (food infection - not food poisoning) so longer incubation period of 7-10 days.

Causes: fever, abdominal cramping, diarrhoea (can be bloody).

Releases a cytotoxin (like cholera).

Can last days to weeks.

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15
Q

What is shigella?

A

A Gram negative rod that causes shigellosis - a dysentery commonly affecting young children.

It is spread form infected stools, person to person - only need a small dose for infection.

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16
Q

Describe the pathophysiology of a shigella infection

A

Invades large intestine colonocytes, multiplies in cells and invades neighbouring cells.

This kills colonocytes and forms abscesses in the mucosa.

17
Q

What are the symptoms of Shigella?

A

Bloody diarrhoea with mucus and abdominal cramping.

18
Q

Describe the pathophysiology of enterotoxigenic E. Coli

A

Invades enterocytes and produces enterotoxins.

Cause hypersecretion go chloride ions

Water leaves cells into the gut lumen - watery diarrhoea

Main cause of travellers diarrhoea.

19
Q

What type of bacteria is Clostridium difficile?

A

Gram positive, anaerobic, spore forming bacillus.

It is a minor component of the GI tract but can be transferred via the faecal-oral route.

Spores are difficult to get rid of from an environment (hospital) -lots of infections)

20
Q

Risk factor for C. Diff?

A

Previous antibiotic therapy -colonise gut and release toxins A&B

Being in hospital - lots of spores.

21
Q

What does a Clostridium difficile infection result in?

A

Antibiotics, especially broad spectrum can precipitate C. difficile proliferation.

Result in:

  • Asymptomatic (most)
  • Varying degrees of diarrhoea (mild to terrible but rarely bloody)
  • Abdominal cramping

Rare (<5%) complications include:

  • Pseudomonas colitis
  • Toxic megacolon (worse case -could need surgery to remove necrotic bowel).
22
Q

What is pseudomonas colitis?

A

A pseudomembrane of the colon.

An inflammatory condition where elevated yellow plaques join to form a pseudomembrane.

23
Q

How do you treat C. Diff?

A

Remove offending antibiotics
Fluid resuscitation
Metronidazole / Vancomycin
Probiotics

24
Q

What is rotavirus?

A

Very common cause of gastroenteritis in under 5s

Double stranded RNA virus spread faecal-orally.

Adults are rarely infected as immunity lasts into adulthood.

Vomiting and fever are first symptoms.

25
Q

How does rotavirus cause diarrhoea?

A

Chloride secretion:

  • creates gradient for movement of Na+ into lumen
  • Water moved by osmosis
  • Diarrhoea

SGLUT1 disruption:

  • Reduced movement of Na / glucose into enterocyte
  • Higher osmotic load in gut
  • Water moves my osmosis

Brush border dysfunction:
-General malabsorption

26
Q

What is norovirus?

A

Most common cause of non bacterial gastroenteritis in the world.

Can affect any age as there are a huge number of strains (no immunity)

Only requires small dose - highly contagious

Virus resistant to cleaning

Incubation = 1-2 days and symptoms last for 1-3 days.

27
Q

What are the symptoms and treatment of norovirus?

A

Symptoms: vomiting, watery diarrhoea, fever
-anion secretion so water movement of water into gut lumen. Vomiting due to delayed gastric emptying.

Treatment: oral rehydration therapy.

28
Q

What parasitic infections cause gastroenteritis?

A

Cryptosporidium - sporozan

Giardia lamblia - flagellate

Entamoeba - amoeba

29
Q

What is cryptosporidium?

A

It is a Protozoa - transmitted by faecal-oral route. But, can also spread via bodies of water infected by animal faeces

30
Q

Doe does cryptosporidium cause diarrhoea?

A

Ingestion of an oocyst (cyst containing a parasite).

This reproduces inside the epithelial cells of the distal small intestine.

Oocytes are excreted in faeces to continue cycle.

It produces a watery diarrhoea that is normally self limiting -malabsorbtion (brush border effected), chloride secretion.

31
Q

What is giardia?

A

Protozoal infection that causes (often persistent) diarrhoea.

Most infections are asymptomatic but symptoms are common in children.

Spread by the faecal-oral route with water supplies often affected.

Lasts a long time (up to 6 weeks!) and 10 day incubation period.

Symptoms (if not asymptomatic): Diarrhoea, Abdominal cramping.

Treated with antibiotics and fluid rehydration therapy.

Lactase deficiency is common post infection as SI damaged so cannot absorb lactose for a bit.

32
Q

Describe the pathophysiology of Giardia

A

Cyst ingested:

  • Stomach acid / pancreas’s enzymes release parasite form cyst which multiplies in SI (2 weeks incubation)
  • Damages proximal SI causing diarrhoea
  • villous atrophy occurs

Parasite then goes back into cyst stage in colon:
-Excreted to repeat the cycle.

33
Q

What is entamoeba histolytica?

A

80% asymptomatic but can cause bloody diarrhoea and liver abscesses and rarely toxic megacolon.

Transmitted faecal-orally

Risk factors:
Poor sanitary conditions
MSM

Treatment:
Anti-protozoals or metronidazole

34
Q

Describe the pathophysiology of entamoeba

A

Infection follows the ingestion of cysts.

Excystation occurs in colon where trophozoites invade mucosa causing bloody diarrhoea and changes similar to IBD.

Infection can also spread to liver -forming abscesses.

Cysts then pass out with faeces -infect others.

35
Q

What is travellers diarrhoea?

A

Diarrhoea is the most common symptom of Tavel related illness.

ETEC is the most common cause globally

Defined as passing 3 or more loose / watery stools per day +/- fever, abdominal pain.

If +14 days of symptoms, less likely to be bacterial.

Only antibiotics if vulnerable (immunocompromised).

36
Q

How are risks of travellers diarrhoea increased?

A

Visit south and east Asia, central America and west and north Africa

Backpacking - dietary exposure

Less than 6 years - PPIs, Blood group O.

37
Q

How do you prevent travellers diarrhoea?

A

Good hand hygiene

Food and water precautions

38
Q

How do you treat travellers diarrhoea?

A

Mild / moderate (<6 stools /24hrs):
Hydration, antidiarrhoeal agents.

Severe (>6 stools/24hours)
IV fluids, antibiotics

ESA 3 - Gastrointestinal System (18 decks)

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