Infectious Diarrhoea Flashcards
What is diarrhoea? What is gastro-enteritis?
Diarrhoea - subjective, describes increase fluidity and frequency
Gastro-enteritis - objective, 3 or more loose stools per day + accompanying features (pain / fever / vomiting etc.)
What is Dysentery?
- Large bowel inflammation
- Blood / mucus in faeces, abdominal cramps, severe diarrhoea
On the stool chart, patients with food poisoning / bacterial gastroenteritis tend to have a score of?
6 or 7
+ additional features such as blood / mucus in stool or abdominal cramping
What are the most common causes of gastroenteritis?
- Viral gastroenteritis (norovirus)
- Campylobacter (commonest pathogen)
- Salmonella (only 1% of cases but causes most hospital admissions)
What are the three types of diarrhoeal illness & an example of each?
- Non-inflammatory - cholera
- Inflammatory - shigella dysentery
- Mixed Picture - C. Difficile
How does non-inflammatory diarrhoea tend to present?
- Frequent watery stools with little abdominal pain
- Minimal, if any, systemic upset / fevers
What is the general mechanism for non-inflammatory diarrhoea pathogens?
Secretory toxin mediated
- Toxin causes excess secretion of water from gut
- Eg. cholera causes increase in cAMP which results in increased Cl secretion, followed by Na / K & water
How does inflammatory diarrhoea tend to present?
- Frequent watery stools + abdominal pain + fever
How is non-inflammatory diarrhoea treated? How is inflammatory diarrhoea treated?
Non-inflammatory - rehydration
Inflammatory: rehydration +/- antimicrobials (rehydration usually sufficient)
What are some important questions when taking a history for suspected gastroenteritis?
- Duration of sickness (if >2 weeks gastroenteritis unlikely)
- Travel history / risks of food poisoning
Clinical examination for suspected gastroenteritis?
- Assess hydration: postural BP / skin turgor / pulse
- Features of inflammation (fever)
- Infants: sunken eyes, dry mouth, sunken fontanelle
Investigations for suspected gastroenteritis?
- FBC (electrolytes / neutrophilia / haemolysis)
- Stool culture / blood culture
- Renal function
- Abdominal X-Ray / CT if abdomen distended
DDx for diarrhoea?
- Inflammatory bowel disease
- Spurious diarrhoea (secondary to constipation - old people)
- Carcinoma
How do you rehydrate a person with gastroenteritis?
- Salt/Sugar solution
- glc. & Na symported in intestine, increasing levels of them increases absorbtion, and water follows electrolytes in
What are some characteristics of Campylobacter Gastroenteritis?
- Up to 7 days incubation period
- Can present with severe abdominal pain
- Not usually invasive, if seen in serum consider underlying pathology
What are some characteristics of Salmonella Gastroenteritis?
- Symptom onset usually within 48hrs of exposure
- Diarrhoea usually lasts <10 days
- Post infectious irritable bowel is common
What are some characteristics of E. Coli O157 Gastroenteritis?
- Characterized by frequent bloody stools
- The E. Coli tends to remain in the gut, but its toxin (shiga toxin) invades the blood
- Can cause haemolytic-uraemic syndrome
What is haemolytic uraemic syndrome?
- Haemolytic anaemia, renal failure & thrombocytopenia (low platelets)
- Caused by toxins stimulating platelet activation within the body (breaks down RBCs as they pass through)
- Treatment tends to be supportive (dialysis etc.)
When are antibiotics indicated in gastroenteritis?
- Immunocompromised patients
- Severe sepsis / septicaemia
- Patients with chronic illness (eg. malignancy)
What are the most common strains of salmonella causing gastroenteritis?
- Salmonella enteritidis
- Salmonella typhimurium
How can C. Difficile present? Why is this?
- Severity ranges from mild diarrhoea to severe colitis (mixed picture between inflammatory & non-inflammatory)
- Because C. Diff produces 2 different toxins: enterotoxin & cytotoxin
Treatment of C. Diff infection?
Metronidazole
oral vancomycin / Fidaxomicin
Stool transplants
surgery may be required
How is infection with parasites (protozoa and helminths) diagnosed?
Diagnosis generally by microscopy
Most common protozoal infection in the UK? Symptoms? Treatment?
- Giardia lamblia
- Abdominal cramps, bloating, nausea and bouts of watery diarrhoea, malabsorption and failure to thrive
- Metronidazole to treat
What are the most common causes of viral diarrhoea?
- Norovirus
- Rotavirus (children under 5yrs)
- Adenovirus (only certain strains)
How infectious is norovirus? What measures are commonly taken when detected? How is it detected?
- Very infectious, isolation & ward closures common when detected
- Diagnosed by PCR
Most common bacterial, parasitic and viral causes of diarrhoea?
- Bacterial gastroenteritis: Campylobacter, Salmonella, E.coli
- Parasitic diarrhoea: Giardia, Cryptosporidium, Entamoeba histolytica
- Viral diarrhoea: rotavirus, adenovirus, norovirus
