GI Infections Flashcards
What is the main defence against infection in the Gi tract?
Commensals organism/normal gut flora
What are some GI defences?
Sight, smell, memory
Salivary (bacteriostatic secretions)
Gastric acid
Bile
Colonic mucus
Anaerobic environment
How does the number of Microbiota change a you progress through the gut?
Proximal gut relatively sterile -> more and more Microbiota
What are the benefits of a micro biome?
Harmful bacteria cant compete for nutrients
Microbiota produce anti microbial substances
Help develop newborns immune system
Produce certain nutrients
What is the main nutrient produced by the micro biome?
Vitamin K
Why are C-section babies more likely to develop infection?
They dont pass all the way through the birth canal so receive less of moms micro biome
How does a less diverse microbiome affect your health?
Obesity more likely
Inflammatory bowel disease
Less likely to respond to chemotherapy
Reduced insulin response to food
What short Chain fatty acids do gut bacteria produce?
Butyrate
Acetate
Propionate
What is the function of the gut bacteria producing the short chain fatty acids like acetate, propionate and butyrate?
Energy source for colonocytes
Cholesterol metabolism (acetate)
Regulating satiety (propionate)
What can affect microbiota in terms of diet and meds?
High fibre (help get rid of bile salts and keeps Microbiota healthy)
Sweeteners (disrupt)
Gluten free diet (without PMH bad)
PPI (inc GI infections)
Antibiotics in meat
Obesity
Probiotics (live bacteria in food)
Prebiotics (food for the Microbiota)
What is a fecal Microbiota transplant?
Take faeces from healthy donors and then give it to sick individuals
Since faces contain many active microbes
How can fecal Microbiota transplants be delivered?
nasogastric tube
Upper GI endoscopy
Colonoscopy
Put in caecum
What disease can Fecal Microbiota transplant be used to treat pretty well?
Clostridium difficile infection
IBD symptoms like Chrons disease
What are the characteristics of the donors for fecal Microbiota transplants?
10 - 25 years
Not having used (last 3months):
-antibiotics
-laxatives
-diet pills
No GI disease
Screened
What are some gram negative bacterial infections of the gut?
Salmonella
Campylobacter
Shigella
Enterotoxigenic ecoli
what is a gram postitive bacteria infection of the GI tract?
Clostridium difficile
What condition does salmonella cause?
Gastroenteritis
What are some symptoms of salmonella infection? (Gastroenteritis)
Nausea
Vomiting
Diarrhoea (mostly non bloody)
Fever
Abdominal cramps
How is salmonella spread?
Ingesting contaminated food or water
What is the pathophysiology of salmonella infection?
Progresses through stomach acid to GI tract
Invades enterocytes (endocytosis)
Body responds which can lead to colitis like presentation
Moves to submucosa and engulfed by macrophages
Macrophages take infection to lymph nodes
Lymphoid hyperplasia
Then they infection can re-enter gut from liver and gall bladder leading to systemic infection
How is salmonella managed?
Usually self limiting )2-3 days)
Fluid resus with electrolytes
How is campylobacter normally spread?
Fecal-oral route usually from poultry
What are the symptoms of campylobacter causing gastroenteritis?
Fever
Abdominal cramps
Diarrhoea (produces cholera like cytotoxin)
How iis campylobacter managed?
Normally self limiting
Fluid/electrolyte replacemtn
Abx if diarrhoea bloody
How is shigella spread?
Infected stools from person to person
What sort of patients does shigella normally infect?
Young children under 5s
What is shigellosis?
A dysentery which normally affects you children
What is the pathophysiology of shigella causing gastroenteritis?
Invades large intestine colonocytes (replaicting and invading neighbouring cells)
Kills colonocytes forming abcesses in mucosa
What are the symptoms of shigella gastroenteritis?
Bloody diarrhoea with mucus
Abdominal cramping
How is shigella usually managed?
Usually self limiting and resolves in a week
What is enterotoxgenic e-coli?
A commensal of the colon but can transform into aa pathogen
How is enterotoxigenic e-coli spread?
Faecal-oral route by contaminated water
What condition does enterotoxigenic e-coli gastroenteritis commonly cause?
Travellers diarrhoea
What is the pathophysiology of enterotoxigenic e-coli infection?
Adheres to enterocyets producing enterotoxins
Enterotoxins cause hypersecretion of chloride ions
Water leaves cells into the gut lumen causing diarrhoea
What is a very good defence against gastroenteritis caused by infection via oral route?
Stomach and the gastric acid
What is the normal route of spread for gram negative Rod bacteria causing gastroenteritis?
Oral route (food, water, faecal)
What symptom do gram negative rod bacterial infections causing gastroenteritis all have?
Diarrhoea
What gram negative bacterial infections causing gastroenteritis produce bloody diarrhoea?
Shigella
Campylobacter
What gram negative bacterial infections causing gastroenteritis produce NON bloody diarrhoea?
Enterotoxigenic e-coli
Salmonella
Why does Shigella nd campylobacter infection lead to bloody diarrhoea?
Affects the large intestine/colon
Why does Enterotoxigenic e-coli and salmonella cause NON bloody diarrhoea?
Usually affects the small intestine
How do all the gram negative rods produce symptoms?
Produce TOXINS
What is HUS?
Haemolytic Uraemic Syndrome
What is Haemolytic Uraemic Syndrome (HUS)?
Triad of:
-anaemia
-thrombocytopenia
-acute kidney injury
Which 2 gram negative rods can cause HUS?
Shigella
Campylobacter
Why are antibiotics carfully given with ram negative Rod infection?
Trying tp avoid resistance
What is the relative duration of the gram negative rod infections causing gastroenteritis?
Enterotoxigenic e-coli (days)
Salmonella (days)
Shigella (weeks)
Campylobacter (weeks)
Which of the gram negative rods that can cause gastroenteritis which one is likely to produce symptoms that last for weeks?
Campylobacter
Which one of the gram negative rods can cause bloody diarrhoea?
Shigella
Campylobacter
What type of organism is Clostridium difficile?
Gram positive
Anaerobic
Bacillus
Forms spores
How is Clostridium difficile spread?
Faecal oral route
Minor component of normal Microbiota
What is usually the main cause of C.difficle infection?
Following antibiotic treatment
What are the 2 types of toxins produced by C.difficle?
Toxins A and B
What type of toxin is Toxin A and Toxin B produced by Clostridium difficile?
A = enterotoxins (excessive secretion and inflammation)
B = cytotoxin (kills coloncytes)
What are the symtoms of C.difficle infection?
Asymptomatic
Varying degrees of diarrhoea
Abdominal cramping
Sometimes:
Pseudomemrabnous colitis
Toxic megacolon
How is toxic megacolon treated?
Surgery
What is pseudomembranous colitis?
Inflammatory condition
Where elevated yellow plaques found in the colon
How is Clostridium difficile infection treated?
Remove offending abx
Fluid resus
Metronidazole/vancomycin
Probiotics
What are the best abx to treat C.diff?
Vancomycin
Metronidazole
What is the major precipating factor in gastroenteritis caused by c.diff?
Abx
In rare cases what can C.difficle infection lead to?
Toxic megacolon
What are some viral causes of gastroenteritis?
Rota virus
Norovirus
What are some parastitic causes of gastroenteritis?
Cryptosporidium
Giardia
Entamoeba
What age group does rota virusgastroenteritis affect?
Under 5s
(Only needs a small dose)
What are the symptoms of rota virus causing gastroenteritis?
Vomiting
Fever
Diarrhoea
How does rota virus cause diarrhoea?
Increased chloride secretion
Disrupts SGLT1 (malabsorption)
Reduced brush border enzyme function
How is rota virus gastroenteritiiis treated?
Fluid replacemtn
How does rota virus affect chloride secretion?
CFTR channels open
Chloride secreted
Na+ follows Cl-
Water follows in gut lumen = diarrhoea
How does SGLT1 disruption cause problems with roots virus gastroenteritis?
Inc diarrhoea
Reduced movemtn of Na/Glucose into enterocyte
Higher osmotic load in gut
Water moves by osmosis
How can we differentiate norovirus to rota virus?
Norovirus can affect any age so cant develop an immunity to it like rota virus
How like does a norovirus infection last?
Usually like 3 day
What part of the gut does norovirus affect?
Small intestine
What symptoms occur with norovirus causing gastroenteritis?
Watery diarrhoea
Vomiting
Fever
What causes the watery diarrhoea with norovirus infection?
Anion secretion into gut lumen leading to water moving into lumen
What causes vomiting in norovirus gastroenteritis?
Delayed gastric emptying
How is norovirus gastroenteritis treated?
Oral rehydration therapy
What are the parasitic causes of gastroenteritis?
Cryptosporidium
Giardia lamblia
Entamoeba histolytica
What is the difference between the 3 parasitic causes of gastroenteritis?
Cryptosporidium = sporozoan so non motile
Giardia lamblia = motile due to flagella
Entamoeba = motile due to amoeba (cytoplasmic projections)
How is cryptosporidium transmitted?
Facial oral route but can survive in bodies of water
Who are normally affected by cryptosporidium?
People in poorly sanitised pools
Parents of infected children
People handling infected cattle
Backpackers and hikers drinking infected water
What is an oocyst?
Cyst containing the parasite which we ingest into the body
Where does the oocyst reproduce once it’s in the body?
Epithelial cells at distal small intestine and then excreted in faces
What are the symptoms of cryptosporidium gastroenteritis?
Watery diarrhoea
Malabsorption
Chloride secretion
How is cryptosporidium gastroenteritis managed?
Supportive (fluids)
Anti parasitics (vulnerable patients)
How does Giardia present?
Asymptomatic (if symptomatic normally affects children)
How is Giardia spread causing gastroenteritis?
Fecal oral route (contaminated water)
What is the rough incubation period leading to symptoms in Giardia?
10+ days
What are some symptoms of Giardia infection?
Diarrhoea (which can be persistent)
Abdominal cramping
What is the 2 stage lifecycle of Giardia?
Cyst ingested:
Stomach acid and pancreatic enymes relase parasite from cyst leading to it multiplying in the small intestine damaging the proximal small intestine
Parasite then goes back into the cyst stage in the colon to be excreted
How is Giardia gastroenteritis treated?
Antibiotics
Fluid rehydration therapy
What deficieny can occur post Giardia infection?
Lactase deficiency
How does entamoeba histolytica infection present?
Most asymptomatic
If symptomatic:
Diarrhoea
Liver abcesses (rare)
How is entamoeba histolytica transmitted?
Faecal oral (from contaminated food or water)
Who does entamoeba histolytica normally affect?
Travel to tropical places that have poor sanitary conditions
Living in poor sanitary conditions
Male intercourse
What is the life cycle of entamoeba histolytica?
Cysts ingested
Protozoa exit cyst in colon (excystation) where the active trophozoites invade the mucosa
Can infect the liver too and then the heart’
Trophozoites enter back into cysts to be passed out as faeces
Are entamoeba histolytica that are passed out in thee cyst form considered infective?
Are entamoeba histolytica that are passed out in thee trophozoite form considered infective?
Cyst form = infective (what we ingest
Trophozoite form = non infective
What is the treatment for entamoeba histolytica?
Antiprotozoals + metronidazole
If they get severe colitis or toxic megacolon surgery needed
What is the most common causative organisms for travellers diarrhoea?
Enterotoxigenic e-coli
What is defined as travellers diarrhoea?
Passing 3 or more loose watery stools
With or without fever or abdominal pain
How long does travellers diarrhoea normally affect a patient?
2 weeks
If ore unlikely bacteria
Who are antibiotics usually given to if they have travellers diarrhoea?
Vulnerable patients
What are the risks of getting travellers diarrhoea?
Place you visit
Diet
On PPIs
Young (<6 yrs)
Blood group O
How can you prevent travellers diarrhoea?
Good. Hand hygiene
Food and water precautions
How do you treat travellers diarrhoe?
Mild/moderate
Mild/moderate (less than 6stools/24hrs)
Hydration (oral with safe water)
Antidiarrhoeal agents
How do you treat severe travellers diarrhoea?
More than 6 stools per 24hrs
IV fluids
Abx if appropriate
