GI infections Flashcards
What is the general GI antibiotic?
Metronidazole
What is dysentery?
Bloody diarrhoea w/ mucus
What is infection of the biliary tract, liver and peritoneum usually a result of?
Spread of colonic flora (e.g. E. coli)
Describe the shape of H. pylori
Gram -ve curved bacillus
How does H.pylori protect itself from stomach acid?
Production of urease (formation of ammonia and CO2 from urea)
How does H. pylori cause gastritis?
Causes a neutrophil influx (pro-inflam cytokines), CagA and VacA genes, ammonia
how does H. pylori cause increased gastric acid production?
Increases parietal cell mass, inhibits D cells and stimulates G cells
What diseases are linked with H. pylori infection?
Gastritis, peptic ulcers, GORD (–> barret’s oesophagus –> oesophageal adenocarcinoma)
What investigations would you do to test for H. pylori infection?
Urea breath test 13C, stool Ag, endoscopy + biopsy
What is the treatment for the eradication of H. pylori?
Omeprazole, amoxicillin + clarithromycin (I.e. 2 Abx + 1 PPI)
What is gastroenteritis?
Infective diarrhoea
What are some of the viral causes of infective diarrhoea?
Rotavirus (infants), norovirus, adenovirus
What are some of the bacterial causes of infective diarrhoea?
E. coli, campylobacter jejuni, salmonella, shigella, C. difficile
What are some parasitic causes of infective diarrhoea?
Cryptosporidium, giardia
What are some non-infective causes of diarrhoea?
Coeliac disease, UC, Crohn’s, malignancy, tropical sprue hyperthyroidism
What is the commonest cause of gastroenteritis (infective diarrhoea)?
Campylobacter jejuni
What E. coli causes bloody diarrhoea? How?
EHEC - shiga-like toxin (1 + 2)
What might you ask in a history if someone presents with diarrhoea?
Food handler? Travel? Pets?
What is the commonest cause of traveller’s diarrhoea?
ETEC
Give 3 parasitic causes of traveller’s diarrhoea?
cryptosporidiosis, giardiasis, amoebiasis
Give a non-infectious cause of traveller’s diarrhoea
Tropical sprue
How would you treat giardia and amoebiasis infections?
Metronidazole
give 6 forms of E. coli?
ETEC, EHEC, EIEC, EPEC, EAEC, DAEC
Which two forms of E. coli are toxin producing? What do they produce?
ETEC (produces LT [heat labile] and ST [heat stable]) and EHEC (shiga-like toxin 1 + 2)
What does ETEC produce - what does this cause?
LT and ST toxins –> increase water loss from enterocytes (watery diarrhoea)
What does EHEC produce - what does this cause?
Shiga-like toxins 1 and 2 –> bloody diarrhoea
What does EIEC do?
It invades enterocytes causing them to die –> bloody diarrhoea
What type of diarrhoea does EPEC produce - how does it do this?
It causes watery diarrhoea by adhering to the intestinal epithelium preventing the absorption of water
What causes C. difficile?
It is an antibiotic associated diarrhoea - antibiotic misuse (such as fluoroquinolones)
How does C. difficile stain?
gram +ve
Does C. difficile produce spores?
Yes
How is C. difficile spread?
Faeco-oral route
What toxins does C. difficile produce? What do they do?
Toxins A and B –> increase permeability of the intestinal epithelium to water by reducing tight junctions between cells
What type of diarrhoea does C. diff produce?
Watery
How would you test for C. difficile?
Stool sample (GDH), ELISA (toxin A + B), tissue culture cytotoxicity assay
What is the GOLD STANDARD investigation for C. difficile?
Tissue culture cytotoxicity assay
What is the 1st and 2nd line antibiotic for C. difficile?
1st: metronidazole
2nd line: vancomycin
What are the features that separate diarrhoea in an immunocompromised host from a healthy host?
In immunocompromised:
- lasts longer
- broader range of causative organisms (such as CMV)
- more severe presentation
What are those who have B cell depletion (e.g. after using rituximab) at risk of? Why?
Giardia (a parasite) due to reduced IgE production
When do HIV patients start to get opportunistic infection? When do they get diarrhoea related infections?
Give a viral, bacterial and parasitic cause of diarrhoea in HIV patients with a CD4 count of
viral (CMV), bacterial (MAC), parasitic (cryptosporidium)
What is unusual about the presentation of cryptosporidium parvum?
No fever
What are the 3 types of liver abscesses?
Bacterial (pyogenic), hydatid cyst and amoebic liver abscess
What are the sites of origin of bacteria that cause pyogenic liver abscesses? Give an example for each
Intestine (E. coli), dental source (K. pneumoniae), biliary tract…
What are the symptoms of a pyogenic liver abscess?
Fever, weight loss, RUQ pain
what are the signs of a pyogenic liver abscesses?
tachycardia, TENDER HEPATOMEGALY, fever
What Ix’s would you do to diagnose a pyogenic liver abscesses?
Blood cultures, US guided percutaneous aspirate
What is the 1st and 2nd line treatment for a pyogenic liver abscesses?
1st line: co-amoxiclav and metronidazole
2nd line: catheter drainage (US guided)
What causes a hydatid cyst? How would you diagnose it?
Dog tapeworm - ELISA serology
What is the treatment for a hydatid cyst?
Drainage + albendazole
What is the treatment for an amoebic liver abscess?
Metronidazole
