Introduction to Infection - Diarrhoea Flashcards
Which bacteria are sought by routine culture of stools from patients with diarrhoea? (3)
Salmonella, campylobacter and E. coli O157
Definition of diarrhoea
(subjective)
An increase in fluidity and frequency of stools
Definition of gastroenteritis
Three or more loose stools in 24 hours
At least one of: fever, vomiting, pain, blood/mucus stools
Definition of dysentery
Large bowel inflammation with bloody stools
Describe the epidemiology of gastroenteritis (4)
- Contamination of livestock/foodstuffs (due to intensive farming)
- Poor storage of produce (i.e. not in fridge)
- Travel related infections
- Person-to-person spread
Defences against enteric infections (5)
- hygiene
- gastric acid
- normal flora
- gut immunity
- gut motility
What are the three “types” of diarrhoea?
- Non-inflammatory/secretory (e.g. cholera, travellers’ diarrhoea)
- Inflammatory (e.g. shigella dysentry)
- Mixed (e.g. C. difficile)
Describe non-inflammatory/secretory diarrhoea
- Usually toxin-mediated
- Frequent watery stools with little abdominal pain
- Rehydration is the mainstay of treatment
Describe inflammatory diarrhoea
- Inflammatory damage and mucosal destruction
- Usually caused by bacterial toxin
- Abdominal pain, bloody stools and systemic upset (fever)
Rehydration and (sometimes) antimicrobials required
How long does diarrhoea due to gastroenteritis usually last?
<2 weeks
How do you assess hydration? (3)
- postural blood pressure
- skin turgor
- pulse
What investigations should be done for suspected gastroenteritis?
- stool culture
- blood culture
- renal function
- blood count - neutrophilia, haemolysis
- abdominal X-ray if abdomen is distended or tender
What is the differential diagnosis for gastroenteritis?
- Inflammatory bowel disease (>2 weeks)
- Spurious diarrhoea (secondary to constipation)
- Carcinoma
- Diarrhoea as part of the response to sepsis (lack of abdominal pain/tenderness and no blood/mucous in stools)
What is the treatment for gastro-enteritis? (3)
- Rehydration (oral sugar/salt solution, or IV saline)
- Possibly antimicrobials
- Treatment of complications
What is the incubation period of campylobacter?
Up to 7 days (so dietary history may be unreliable)
What are some of the clinical features of campylobacter gastroenteritis? (4)
- Severe abdominal pain
- Rarely invades into bloodstream (<1%)
- Clears within 3 weeks
- Post-infection sequelae such as Guillian-Barre syndrome and reactive arthritis
What is the typical onset and duration of symptoms of salmonella gastroenteritis?
- Onset usually <48 hours after exposure
- Diarrhoea usually lasts <10 days
What are some other clinical features of salmonella gastroenteritis? (4)
- Commonest pathogens are Salmonella enteritidis and Salmonella typhimurium
- <5% positive blood cultures
- 20% patients still have positive stools 20 weeks post-infection
- Post-infectious irritable bowel is common
How does E. coli O157 infection spread?
- Contaminated meat
- Person-to-person (low inoculum)
Which symptom differentiated E. coli O157 infection from campylobacter or salmonella infection?
Frequent BLOODY stools
Describe the pathogenesis of E. coli O157 gastroenteritis
- E. coli O157 produces verocytotoxin(s)
- Toxin (NOT bacteria) enters the blood
- Can cause haemolytic-uraemic syndrome (HUS), particularly in children and the elderly
- 5-9 days between onset of diarrhoea and HUS
What is haemolytic-uraemic syndrome (HUS)?
- Toxin causes platelet activation and micro-angiopathy
- Leads to renal failure, haemolytic anaemia and thrombocytopenia
Which other bacteria (apart from campylobacter, salmonella and E. coli O157) can cause gastroenteritis? (7)
- Shigella
- Clostridium difficile
- Other forms of E. coli
- Cholera
- Staphylococcus aureus (toxin)
- Bacillus cereus (refried rice)
- Clostridium perfringens (toxin)
What are the indications for treatment of gastroenteritis with antibiotics? (5)
- Immunocompromised patient
- Severe sepsis or invasive infection
- Valvular heart disease
- Chronic illness
- Diabetes
Which bacteria typically cause travellers’ diarrhoea?
Enterotoxigenic E. coli
What are the “4C antibiotics” typically associated with Clostridium difficile diarrhoea?
Cephalosporins
Co-amoxiclav
Clindamycin
Ciprofloxacin
(also possibly clarithromycin)
What are possible treatments for C. difficile diarrhoea? (4)
- Metronidazole
- Oral vancomycin
- Stool transplants
- Surgery
What are the common parasites which cause diarrhoea in the UK?
- Giardia lamblia (diarrhoea, malabsorption)
- Cryptosporidium parvum (no treatment)
- Entamoeba hystolitica (amoebic dysentery - “anchovy pus” liver abscess)
What is the most common viral enteropaths?
Rotavirus and norovirus
