Infectious Diarrhoea Flashcards
What is clinical definition of gastro-enteritis?
- three or more loose stools/day - accompanying features
What is dysentery?
- large bowel inflammation, bloody stools
What are the 7 types of faeces on the bristol stool chart?
Type 1 - separate hard lumps Type 2 - Sausage shaped but lumpy Type 3 - sausage shaped but cracked Type 4 - like a sausage or snake, smooth Type 5 - soft blobs with clear cut edges Type 6 - fluffy pieces with ragged edges Type 7 - entirely liquid
What are the 4 common causes of gastroenteritis?
- contamination of food stuffs - poor storage of food stuffs - travel related infections - person to person spread
What is the most common causative pathogen of gastroenteritis?
Viruses are commonest cause with campylobacter being the commonest bacterial pathogen.
Which pathogen causes the most hospital admissions per year?
Although campylobacter is the most common causative pathogen, salmonella causes the most admissions per year (around 2500)
Which food is most commonly linked with food poisoning?
- Poultry meat
Which pathogen causing GE is on the rise?
E. Coli
What are the 4 main defences we have against enteric infections?
- Hygiene - Stomach acidity - Normal flora - Immunity
What 3 different types of diarrhoeal infection?
- Non-inflammatory/secretory (cholera) 2. Inflammatory (shigella dysentery) 3. Mixed picture (c. difficile)
What causes the effects in non-inflammatory diarrhoeal infection?
It is secretory toxin mediated: causes rise in cAMP and Cl secretion.
What are the symptoms of non-inflammatory diarrhoea? Tx?
- Frequent watery stools with little abdo pain - oral rehydration salts
What causes the effects in inflammatory diarrhoea?
Inflammatory toxin damage and mucosal destruction
What are the symptoms of inflammatory diarrhoea? Tx?
- Diarrhoea, pain and fever - Antimicrobials may be appropriate but rehydration alone is often sufficient
What are RF for food poisoning?
BBQ (dietary) Contact Travel history
How long does it take for suspection of infective gastro-enteritis?
10-14 days at least, some hospitals will not admit until past this threshold
How do we access hydration?
Postural BP Skin turgor Pulse
What are common findings on assessment for infective gastro-enteritis in infants?
Sunken eyes and cheeks Sunken fontanelles Sunken abdomen Few or no tears Decreased skin turgor Dry mouth
What is lost from the body during severe secretory diarhoea?
1-7 l fluid per day containing 80-100 mmol Na Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)
What are the investigations for diarrhoea?
3 stool cultures until satisfied. Blood are rarely positive Renal functions will check how sodium is doing Haemolysis is useful as will show haemolytic anaemia
DDx for diarrhoea?
- IBD - Spurious diarrhoea (secondary to constipation) - Carcinoma
Tx for diarrhoea?
Depending on severity - oral rehydration salts (H2O + salt + glucose) - IV fluids
What are symptoms of campylobactor infection?
abdominal pain can be severe <1% invasive
How are different strains of pathogen identified?
- difficult to find pathogen in the midst of complex normal flora - selective and enrichment methods of culture necessary - variety of media and incubation conditions - takes 3 days to complete all tests
What are signs and symptoms of salmonella gastroenteritis?
- symptom onset usually <48 hrs after exposure - diarrhoea usually lasts <10 days - <5% positive blood cultures - 20% patients still have positive stools at 20/52 - Prolonged carriage may be associated with gallstones - Post-infectious IBS is common
How can we differentiate out the different sub-species of salmonella?
Salmonella is a non-lactose fermenter Salmonella remains a beige colour on agar Only way to separate out sub-species of salmonella is by looking at the antigens
What are the most common strains of salmonella in the UK?
Salmonella enteritidis and Salmonella typhimurium
How does E. Coli spread?
contaminated meat or person-to-person spread (low incoulum)
What is E coli illness characterised by?
Typical illness characterised by frequent bloody stools
What can the E. coli toxin cause?
Toxin can cause hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure). HUS: renal failure, haemolytic anaemia and thrombocytopenia. Treatment supportive – antibiotics NOT indicated
When are antibiotics indicated in gastroenteritis?
immunocompromised severe sepsis or invasive infection valvular heart disease chronic illness diabetes
What causes a clostridium difficile infection?
Some gut bacteria will be effected by antibiotics – this causes inbalance which will allow c diff infection
What are the main drivers of inflammation on a c.diff infection?
Produces toxins which are thought to be the main drivers of inflammation
How can we avoid c.diff infection?
Reduction in broad spectrum antibiotic prescribing Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, clarithromycin
What is the management of c.diff infection?
Stop precipitating antibiotic (if possible) Follow published treatment algorithm – oral metronidazole if no severity markers Oral vancomycin if 2 or more severity markers
What is a protozoa?
single cell parasite
What is a helminth?
worm parasite
How do we diagnose parasites?
Send stool with request “parasites, cysts and ova please” or P, C and O
What is the UK parasite? How does it infect and what are the symptoms?
Giardia Lamblia - contaminated water - diarrhoea, malabsorption and failure to thrive
What are the causes of viral diarrhoea?
Adenovirus Rotavirus in children under 5 Norovirus
How is norovirus diagnosed?
Diagnosis by PCR - ward closures are common - strict infection measures needed
