Gastroenteritis & infectious colitis Flashcards
Define gastroenteritis.
Acute inflammation of the GI tract, manifested by nausea, vomiting, diarrhoea and abdominal pain.
What is the epidemiology of gastroenteritis?
Common, and often under-reported, a serious cause of morbidity and mortality in the developing world.
What is the aetiology of gastroenteritis?
Can be caused by viruses, bacteria, protozoa, or toxins contained in contaminated food or water. Can be caused by inflammatory or non-inflammatory toxins.

List 3 viral causes of gastroenteritis.
- Rotavirus
- Adenovirus
- Astrovirus
- Calcivirus
List 3 bacterial causes of gastroenteritis.
- Campylobacter jejuni
- E coli (0157)
- Salmonella
- Shigella
- Vibrio cholerae
- Listeria
- Yersinia enterocolitica
Name a protozoal cause of gastroenteritis.
- Entamoeba histolytica
- Cryptosporidium parvum
- Giardia lamblia
Name 3 toxins that cause gastroenteritis.
- Staphylococcus aureus
- Clostridium botulinum
- Clostridium perfringens
- Bacillus cereus
- Mushrooms
- Heavy metals
- Seafood
What is the difference between the organisms which cause:
a) diarrhoea
b) dysentery
in bacterial gastroenteritis?
NB: diarrhoea = loose stools
dysentery = bloody loose stools (CHESS organisms)

In bacterial gastroenteritis with diarrhoea, what clues might you get from the history with regards to the responsible organism?

In bacterial gastroenteritis with dysentery, what clues might you get as to the causative organism?

What are some non-inflammatory mechanisms of gastroenteritis?
Non-inflammatory - e.g. V cholerae, enterotoxigenic E. coli produce enterotoxins that cause enterocytes to secrete water and electrolytes.
Describe an inflammatory mechanism causing gastroenteritis.
Inflammatory mechanisms e.g. Shigella, enteroinvasive E. coli release cytotoxins and invade and damage the epithelium, with greater invasion and bacteraemia in the case of Salmonella typhi.
What is the typical presentation of gastroenteritis?
- Sudden onset nausea, vomiting, anorexia
- Diarrhoea (bloody or watery)
- Abdominal pain/discomfort,
- Fever and malaise
- Enquire about recent travel, antibiotic use and recent food intake (how cooked, source and whether anyone else is ill)
Effect of toxins: botulinum causes paralysis, mushrooms can cause fits, renal or liver failure.
What are the signs of gastroenterits on physical examination?
- Diffuse abdominal tenderness
- Abdominal distension
- Bowel sounds are increased
CHECK FOR:
- Mucous membranes, skin turgor, cap refill for DEHYDRATION
- HR, BP – for SHOCK
- Temperature
These indicate severe disease.
What is the typical time of onset of gastroentritis?
- Toxins (early, 1-24 hours)
- Bacterial/viral/proozoal (12h or later)
What investigations would you do for gastroenteritis?
Bedside:
- Stool sample - MC&S - bacterial pathogens, ova cysts (eggs), parasites
- Blood - FBC, blood culture (helps identification if bacteraemia present), U&Es (low K in severe D&V)
Imaging:
- AXR/US - excludes other causes of abdominal pain
Invasive:
- Sigmoidoscopy - unnecessary unless IBD needs to be excluded
What is the management of gastroenteritis?
- Bed rest, fluid and electrolyte replacement with oral rehydration solution (containing glucose and salt)
- IV rehydration may be necessary in those with severe vomiting
- Most infections are self limiting
- Antibiotic treatment only warranted if severe or the infective agent has been identified e.g. ciprofloxacin against Salmonella, Shigella, Campylobacter
Other:
- Botulism - botulinum antitoxin IM and manage in ITU
- PUBLIC HEALTH - often notifiable disease.
- Educate on basic hygiene and cooking

What are the complications of gastroenteritis?
- Dehydration
- Electrolyte imbalance
- Prerenal failure
- Secondary lactose intolerance - particularly in infants
- Sepsis and shock (particularly Salmonella and Shigella)
- Haemolytic uraemic syndrome - associated with toxins from E coli 0157
- Guillain-Barre syndrome may occur weeks after recovery from Campylobacter gastroenteritis
- Botulism –> respiratory muscle weakness/paralysis
What is the prognosis in gastroenteritis?
Generally good
Majority of cases are self-limiting
Which organism causes rice water diarrhoe?
Vibrio cholera
Difference between causes of gastroenteritis with salmonella vs campylobacter?
Salmonella - from uncooked eggs
Campylobacter - uncooked poultry/raw meat
Common cause of diarrhoea associated with antibiotic use?
C diff
Which of these features do not suggest gstroenteritis?
- Streak of blood in vomiting
- Large amount of blood in vomit
- Intermittent abdominal pain
- Constant, worsening/severe abdominal pain
- Blood in stool
- Mucus in stool
2 and 4
What is the management of C difficile?
Non-severe C difficile:
- Metronidazole 400mg PO TDS 10-14days
- If no response in 72hrs change to: Vancomycin 125mg PO QDS 10-14days
Severe C difficile:
- Vancomycin 125mg PO QDS 14 days + consider adding metronidazole 500mg IV TDS
- Specialist advice
If colonic dilatation present:
- Vancomycin 125-250mg PO QDS + metronidazole 500mg IV TDS 14 days
If ileus/vomiting:
-
Consider intracolonic vancomycin
* Fidaxomycin is a new drug associated with fewer relapses so may be increasingly used*
Recurrence in:
<12 weeks = oral fidaxomicin
>12 = oral vanc or fidaxomicin
Other:
- bezlotuxumab
- faecal microbiota transplant
What is the MOA of bezlotoxumab?
mAb against toxin B in C diff
What is the MOA of fidaxomicin?
Inhibiting bacterial RNA polymerase at transcription initiation
How is C diff colitis diagnosed?
TOXIN detection in stool
NB: antigen positivity only shows exposure to C difficile rather than current infection
How is C diff severity categorised?
Imperial C. difficile guidelines
- T>38.5ºC
- HR>90
- WCC>15
- Rising Creatinine
- Clinical or radiological signs of severe colitis
- Failure to respond to therapy at 72h
Severe = 1 or more of the following –> early surgical and gastroenterology review
DIARRHOEA is not part of the criteria
Other than antibiotics what can increase risk of C difficile?
PPIs
Abx:
- Antibiotics use
- 65+ years (many children colonised but do not get problems)
- Duration of hospital stay (after 4 weeks, half of patients become positive)
- Severe underlying diseases
- Almost always associated with a recent history of antibiotic use (clindamycin, cephalosporin, ciprofloxacin)
What 3 antibiotics are the biggest risk factors for C diff?
cephalosporins, ciprofloxacin and clindamycin
Why is diarrhoea not part of the criteria of C diff severity?
You can get ileus and toxic megacolon in very severe disease
What is the pathophysiology of C diff?
Epithelial cells are damaged by the cytotoxin
Disrupts tight junctions
Causing pseudomembranous colitis with fibrous plaques
What are some measures for prevention of C diff infections?
- Hand hygiene with soap and water
- Isolation
- Use of PPE
- Enhanced environmental cleaning (with chlorine)
- Only use narrow-spectrum where possible
What are faecal cultures routinely tested for?
- Salmonella
- Shigella
- E. coli O157
- Campylobacter
- C. difficile toxin – only tested for in those <65 years, need to ask otherwise
How transmissible is C diff?
1g faeces = 1 billion spores so very transmissible