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Gastrointestinal System > GI Infections > Flashcards

GI Infections Flashcards

1
Q

What defences does the GI tract have against infection

A

Saliva - bacteriostatic secretions

Gastric acid

Small intestine secretions

Colonic mucus

Anaerobic environment

Flora in gut

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2
Q

What short chain fatty acids do bacteria in the colon produce

A

Butyrate - energy source for colonocytes. Helps regulate gut environment

Acetate - cholesterol metabolism

Propionate - regulates satiety

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3
Q

What substances are good for the microbiota of the gut and what substances are harmful for it

A

Good:

  • Probiotics - stimulate growth of bacteria in get
  • Prebiotics - used as food for microbiota

Harmful:

  • Sweeteners - disrupt diversity of microbiota
  • Gluten free diet in people without gluten sensivitiy or coeliac disease - decreases number of bacteria species
  • Proton pump inhibitors
  • Antibiotics
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4
Q

Name some bacterial infections of the GI tract

A

Salmonella

Campylobacter

Shigella

Enterotoxigenic E. coli

Clostridium difficile

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5
Q

Describe salmonella - what it is, what it does inside the patient and how it spreads

A

Salmonella is a gram -ve rod

Spread by ingesting contaminated food/water

Is self limiting

Inside gut salmonella gain access to enterocytes -> move to submucosa where the encounter macrophages

Macrophages transfer salmonella to RES where they multiply intracellulary causing lymphoid hypertrophy and hyperplasia

Then re-enter gut from liver/gallbladder

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6
Q

What symptoms do salmonella infections cause

A

Nausea

Vomiting

Diarrhoea - mostly non-bloody

Fever

Abdominal cramping

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7
Q

Describe camplyobacter, how it causes disease, how it spreads and what its treatment is

A

Campylobacter is a gram -ve rod - spiral shaped

Spread via faecal-oral route

Releases cytotoxin to cause disease

Treatment - fluids/electrolyte replacement and antibiotics if bloody diarrhoea

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8
Q

What are the symptoms of a camplyobacter infection

A

Fever

Abdominal cramping

Diarrhoea - can be bloody

Symptoms take a while to appear

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9
Q

Describe shigella, how it causes disease and how it is spread

A

Shigella is a gram -ve rod. Infection usually resolves within a week

Causes shigellosis - dysentery commonly affecting young children

Spread via infective stools

Shigella invades large intestine colonocytes -> multiplies intracellularly -> invades neighbouring cells

This kills colonocytes and forms abscesses in mucosa

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10
Q

What are the symptoms of a shigella infection

A

Bloody diarrhoea with mucus

Abdominal cramping

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11
Q

Describe enterotoxigenic E. coli, how it is spread, what symptoms it causes and how it causes disease

A

ETEC is a gram -ve rod that causes gastroenteritis with symptoms of watery diarrhoea

Spread via faecal-oral route

Common commensual of gut

Invades enterocytes -> produces enterotoxins which cause hypersecretion of Cl -> Na follows -> water follows

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12
Q

What is haemolytic uraemic syndrome and what bacterial infections of the gut can cause it

A

Haemolytic ureamic syndrome is condition affecting blood and blood vessels. Have destruction of platelets, anaemia and kidney failure due to damage to small vessels of the kidney

Shigella and camplyobacter can cause it

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13
Q

Describe C. diff, how it is spread, how it causes disease and what the treatment is

A

C. diff is a gram +ve anaerobic, spore forming, bacillus

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

Following antibiotic therapy, C. diff can colonise the gut and release toxins A and B

Toxin A causes excessive secretion and inflammation

Toxin B is a cytotoxin

Treatment - remove offending antibiotic, fluid resuscitation, metronidazole/vancomycin, probiotics

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14
Q

What are the symptoms of a C. diff infection

A

Can be asymptomatic

Diarrhoea

Abdominal cramping

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15
Q

What are the causes of viral gastroenteritis

A

Rotavirus

Norovirus

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16
Q

What are the symptoms of gastroenteritis caused by rotavirus and how are the symptoms caused

A

Common cause of gastroenteritits in under 5s

Symptoms: vomiting, diarrhoea and fever

Diarrhoea caused by chloride secretoin, SGLT1 disruption and brush border enzyme dysfuction

Treatment is to manage dehydration

17
Q

Describe gastroenteritis caused by norovius and the symptoms that are seen

A

Norovirus is most common cause of non-bacterial gastroenteritis

Affects any age due to large number of strains

Infects small intestine and damages microvilli

Symptoms: vomiting, watery diarrhoea and fever

Causes anion secretion (diarrhoea) and delayed gastric emptying (vomiting)

Treatment is oral rehydration

18
Q

Name some protozoal causes of diarrhoea

A

Cryptosporidium

Giardia

Entamoeba histolytica

19
Q

Describe cryptosporidium, how it is transmitted, how it causes disease, the symptoms and treatment for it

A

Protozoa transmitted via faecal-oral route - can also survive and spread in water

Is caused by ingestion of oocyst containing the parasite which reproduces inside epithelial cells of distal small intestine -> oocysts excreted in faeces to continue cycle

Symptoms of watery diarrhoea (malabsorption and Cl secretion)

Self-limiting

Treatment: supportive but can give anti-parasitic treatment to at risk patients

20
Q

Describe giardia, how it is spread, how it causes disease, what its treatment is and what symptoms it causes

A

Protozoal infection causing diarrhoea - common cause of persistant diarrhoea

Spread via faecal-oral route

Symptoms appear after 10+ days: diarrhoea, abdominal cramping

Cyst is ingested -> stomach acid/pancreatic enzymes release parasite -> it multiplies in small intestine - damaged proximal small intestine

Parasite forms a cyst in colon -> excreted to repeat cycle

Treatment - antibacterial and fluid rehydration

21
Q

Describe entamoeba histolytica, how it is spread, how it causes disease, its symptoms and how it is treated

A

Protozoal infection with high prevalence in developing countries

Spread via faecal-oral route

Infection follows ingestion of cyst - excystation occurs in colon where trophozoites invade mucosa causing bloody diarrhoea and inflammatory changes

Symptoms: asymptomatic or bloody diarrhoea

May have liver abscess if infection spreads to liver

Treatment is antiprotozoal/metronidazole

22
Q

What is travellers diarrhoea

A

Passing 3 or more loose/watery stools

Can have fever and/or abdominal pain

>14 days makes it unlikely to have bacterial cause

Prevention is good hand hygeine and food/water precautions

23
Q

Which patients have increased risk of travellers diarrhoea

A

Patients visiting developing countries

Patients dietary exposure

Patients <6yrs

Patients on PPIs

Patients with blood group O

24
Q

What is the treatment for traveller’s diarrhoea

A

Mild/moderate = <6stools/24hrs. Treatment is hydration and antidiarrhoeal agents

Severe = >6stools/24hrs. Treatment is IV fluids and antibiotics if appropriate

Gastrointestinal System (15 decks)

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