Gastrointestinal Infections Flashcards
(38 cards)
What are our GI defences against illness?
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)
What are the benefits of the microbiome?
Harmful bacterial cannot compete for nutrients
Microbiome produces antimicrobial substances
Helps to develop newborn’s immune system
Produce certain nutrients (vitamin k)
What do gut bacteria produce?
SCFAs - acetate, propionate, butyrate
Butyrate - energy source for colonocytes, helps regulate gut environment
Acetate - Involved in cholestrol metabolism
Propionate - helps regulate satiety
How is the gut microbiome related to health?
Obese and IBD- less diverse population of bacteria.
Microbiome composition affects response to chemotherapy and insulin response to food
What things influence the gut microbiota?
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
What is FMT?
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.
Where can faeces be transplanted?
NG / duodenal tubes - under anaesthetic
Upper GI endoscopy
Colonoscopy
Transplant can be put in caecum (allowed to be moved throughout the colon)
Describe some uses of FMT
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
Where do we get the faeces from?
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.
Describe the symptoms of salmonella
Nausea, vomiting, diarrhoea (mostly non-bloody), fever, abdominal cramping.
It is self limiting
How is salmonella spread?
Ingesting contaminated food / water (symptoms develop 48hours later).
How does salmonella infect (inside gut)?
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.
What is Campylobacter?
It is a spiral or S shaped gram negative rod that causes gastroenteritis.
It is mainly microaerophilic (does not ferment carbs)
Describe a typical campylobacter infection
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.
What is shigella?
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.
Describe the pathophysiology of a shigella infection
Invades large intestine colonocytes, multiplies in cells and invades neighbouring cells.
This kills colonocytes and forms abscesses in the mucosa.
What are the symptoms of Shigella?
Bloody diarrhoea with mucus and abdominal cramping.
Describe the pathophysiology of enterotoxigenic E. Coli
Invades enterocytes and produces enterotoxins.
Cause hypersecretion go chloride ions
Water leaves cells into the gut lumen - watery diarrhoea
Main cause of travellers diarrhoea.
What type of bacteria is Clostridium difficile?
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)
Risk factor for C. Diff?
Previous antibiotic therapy -colonise gut and release toxins A&B
Being in hospital - lots of spores.
What does a Clostridium difficile infection result in?
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).
What is pseudomonas colitis?
A pseudomembrane of the colon.
An inflammatory condition where elevated yellow plaques join to form a pseudomembrane.
How do you treat C. Diff?
Remove offending antibiotics
Fluid resuscitation
Metronidazole / Vancomycin
Probiotics
What is rotavirus?
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.
