Infectious diarrhoea part 1 (plus a bit of part 2 by accident) Flashcards
What symptoms are hallmark of diarrhoea?
Increased fluidity and frequency of stools
Describe the bowel habit seen with gastroenteritis?
3 or more loose stools/day
Will have accompanying features/symptoms
Describe the bowel habit seen with dysentery?
Quite obvious
Large bowel inflammation with bloody stools
What causes infectious diarrhoea?
1) Contamination of foodstuffs
* Intensively farmed chicken and campylobacter
2) Poor storage of produce
* Ie storing food at room temperature causing bacterial proliferation
3) Travel-related infections e.g. Salmonella
4) Person-to-person spread e.g Norovirus
Give an example of a cause of infectious diarrhoea that is spread through person to person contact
Norovirus
What causes infectious diarrhoea, viruses or bacteria?
Viruses are commonest cause with campylobacter being the commonest bacterial pathogen
What are the most common food-borne pathogens?
(ie the ones that cause food poisoning)
Campylobacter is the most common foodborne pathogen
Salmonella is the pathogen that causes the most hospital admissions
What type of meat is most linked to food poisoning?
Poultry
(Chiquen and turkey)
What age group is most at risk of getting/dying of infectious diarrhoea?
Where in the world is the mortality rate highest?
Children
death rate highest in certain parts of Africa
What strain of E.coli is famously pathogenic?
E.coli O157
What are the defences against enteric infections?
Hygiene
Stomach acidity
Normal gut flora
Immunity
What are the types and features of non-inflammatory infectious diarrhoea?
Examples of non-inflammatory ID causing organisms:
- Cholera - (Vibrio cholerae)
- E.coli - (travellers diarrhoea)
Frequent, watery stools with little abdominal pain
What is the general approach to treating non-inflammatory infectious diarrhoea?
Rehydration therapy
Describe the mechanism of diarrhoea in cholera?
Cholera increases cAMP levels inside of epithelial cells
Increased cAMP results in loss of Cl- from cells along with Na+ and K+
Osmotic effect leads to massive water loss into the lumen (ie diarrhoea)
Describe the clinical features of diarrhoeal illness and what causes these features
Watery, frequent stools - for aforementioned reason
Inflammatory toxin damage and mucosal destruction causes PAIN and FEVER
How do assess patients with infectious diarrhoea?
Symptoms and duration
Risk of food poisoning - travel, diet, contact
Assess hydration - postural BP, skin turgor, pulse
Features of inflammation (SIRS) - fever, raised WCC
What features on examination of a neonate may indicate infectious diarrhoea?
Fever etc
Decreased skin turgor
Sunken eyes and cheeks
Sunken fontanelle
Dry mouth or tongue
Sunken abdomen
What is the effect of diarrhoea on fluid and electrolyte balance?
Can cause severe loss of fluid and electrolytes
Which causes Hyponatraemia and Hypokalaemia
How much fluid can patients lose with severe diarrhoea?
How much Sodium?
How much Potassium?
1 - 7 Litres of fluid containing 80 - 100 mmol Na+
Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)
What investigations are done to assess patients with infectious diarrhoea?
- Stool culture +/- molecular or Ag testing
- Blood culture
- Renal function
- Blood count - neutrophilia, haemolysis (E. Coli O157)
- Abdominal X-Ray/CT if abdomen distended, tender
What are the differential diagnoses for infectious diarrhoea and why?
Inflammatory bowel disease
Spurious (overflow) diarrhoea
Carcinoma
Diarrhoea and fever occurring secondary to sepsis outside of the gut
What is spurious diarrhoea?
Diarrhoea secondary to constipation
Hx of alternating constipation & diarrhoea
Usually in elderly people
If a patient presents with severe diarrhoea and fever - how would you differentiate between infectious diarrhoea or sepsis outside of the gut?
Lack of abdominal pain/tenderness
- this goes against Gastroenteritis
No blood/mucus in stool
- would show lack of inflammation etc of intestinal mucosa
How is Gastroenteritis (infectious diarrhoea) treated?
Rehydration therapy:
- Oral rehydration solution - NaCl & glucose solution
- or IV Saline
Antibiotics sometimes needed for infectious gastroenteritis depending on the organism
What features are indicative of campylobacter gastroenteritis?
All the normal symptoms + severe abdominal pain
Incubation period of up to 7 days - so dietary history may be unreliable
What other conditions can arise after campylobacter gastroenteritis?
Guillain-Barre syndrome
Reactive arthritis
What two species of Campylobacter cause the most cases of C. gastroenteritis in the UK?
C. jejuni (90%)
C. coli (9%)
How are campylobacteria transmitted/caught?
Chiquens
Milk
Puppies
Commonest cause of bacterial food poisoning in the UK
What characterises infection with E.coli O157?
Typical illness characterised by frequent bloody stools
What is Shiga toxin?
It is the toxin produced by E.coli O157 and Shigella spp.
E. coli O157 stays in the gut but Shiga toxin is what gets into the blood
Shiga toxin can cause Haemolytic-uraemic syndrome (HUS)
What is haemolytic-uraemic syndrome?
Syndrome caused by Shiga toxin - usually following E.coli diarrhoea
Characterised by:
- Renal failure
- Haemolytic anaemia
- Thrombocytopenia
Most common cause of acute renal failure in children
What other symptoms would be seen in Haemolytic uraemic syndrome?
The symptoms caused by the infection/Shiga toxin in the first place:
- Bloody diarrhoea
- Abdo pain
- Fever
- Seizures
- Lethargy
What is the treatment route for HUS?
Mainly supportive:
IV fluids
blood transfusion
dialysis if required
Antibiotics not indicated
What are the less common causes of food poisoning (and all this infectious diarrhoea stuff)
Staph aureus - (toxin)
Bacillus cereus - (re-fried rice)
Clostridium perfringens - (undercooked meat/cooked food left out - toxin accumulates in spore formation)
When should antibiotics be prescribed for infective gastroenteritis?
Indicated in gastroenteritis if:
- Immunocompromised
- Severe sepsis or invasive infection
- Chronic illness - ie malignancy
Not indicated for healthy person with non-invasive infection
Clostridium difficile infection is a rarer infection which is potentially serious
What causes it?
How severe can it be?
C.diff diarrhoea
Happens following broad spectrum antibiotic treatment (4 C’s - incl clindamycin, cephalosporins)
Ranges from mild diarrhoea to severe colitis - sometimes requiring surgery
What toxins do C.diff produce?
enterotoxin (A) and cytotoxin (B) (inflammatory)
How can Clostridium difficile infection treated?
Oral Metronidazole - first line
Oral Vancomycin - if severe/not responding to Metronidazole
Bezlotoxumab - alternative
