Infectious diarrhoea Flashcards
How is diarrhoea defined?
Increased frequency and fluidity as defined by the patient - subjective
How is gastro-enteritis defonined?
Objectively defined as 3 or more loose stools per day with accompanying features
What accompanying features come with gastro-enteritis?
Abdominal pain
Blood in stool
What is dysentry?
Large bowel inflammation with blood stools
What are the 7 stages on the bristol stool chart?
- Seperate hard lumps
- Sausage shaped but lumpy
- Sausage shaped with cracks on the surface
- Like a sausage, smooth and soft
- Soft blobs with clear cut edges
- Fluffy pieces with ragged edges - mushy
- Entirely liquid
What is the epidemiology of gastro-enteritis?
Contamination of food stuffs
Poor storage of produce
Travel related infections
Person to person spread
What is the most common bacterial organism to cause gastroenteritis?
Campylobacter
What food is the most common cause of food poisoning?
Undercooked chicken
What is the most common cause of GI infection?
Viruses
What pathogen causes the most food poisoning hospital admissions each year?
Salmonella
What defences do we have against enteric infections?
Hygiene
Stomach acidity
Normal gut flora
Immunity
What can have adverse effects on stomach acidity’s effect on defence against enteric infections?
Antacids and infections - raise pH
What are the 2 main types of diarrhoeal illness?
Secretory/non inflammatory - cholera
Inflammatory - Shigella dysentry
What is the difference between secretory and inflammatory diarrhoea at presentation?
Secretory is enormous volumes of watery stool with generally no other systemic upset, inflammatory may have other symptoms such as blood in the stool
What is the mechanism for secretory diarrhoea?
Secretory toxin-mediated - Increased cAMP levels and chloride secretion
How is non inflammatory diarrhoeal illness treated?
Rehydration - little role for antimicrobials
How does inflammatory diarrhoea typically present?
Diarrhoea with abdominal pain and fever
How is inflammatory diarrhoea treated?
Rehydration alone is often sufficient but antimicrobials may also be appropriate
How long does a gastroenteric infection typically last?
Less than 2 weeks
What drop in postural blood pressure would you indicate dehydration?
20mmHg from lying to standing
What should you assess patients for when they present?
Symptoms and their duration
Risk of food poisoning
Hydration
Features of inflammation
What factors could put a patient at risk of food poisoning?
Diet
Contact
Travel history
How is hydration of patients assessed?
Check postural change in BP
Skin turgor
Pulse - check for tachycardia
What features of inflammation would you look for in a patient?
Fever
Raised WCC
What features would a dehydrated infant show?
Sunken eyes and cheeks Sunken fontanelle Few/no tears Decreased skin turgor Dry mouth or tongue
Why is it important to make sure fluid given to patients with secretory diarrhoea has plenty of electrolytes?
They lose a lot of electrolytes as a result of cAMP activating so these must be replaced to avoid hyponatraemia
What assessments can be done on the patient?
Stool culture Blood culture Renal function Blood count Abdominal X-Ray/CT if distended or tender abdomen
What blood counts should be done?
Neutrophilia
Haemolysis
Electrolytes
How many stool samples is typically recommended for culture?
3
Why should imaging be done on a patient with distension/tenderness?
They may be at risk of perforation
What are differential diagnoses for infectious diarrhoea?
IBD
Spurious diarrhoea - secondary to constipation
Carcinoma
Diarrhoea can occur with sepsis outside the gut
What would differentiate diarrhoea caused by sepsis?
Lack of abdominal pain/tenderness
No blood/mucous in stool
What is oral rehydration therapy?
Drinking water with salts to restore both fluid and electrolyte balance
Why does oral rehydration have glucose in it?
Not all salt would be absorbed, but the gut has a sodium glucose cotransporter, which allows more sodium to be absorbed with glucose
What are characteristics of campylobacter gastroenteritis?
7 days incubation, dietary history may be unreliable
Stools negative within 6 weeks
Can have severe abdominal pain
Almost never invasive into blood
What condition can happen post infection of campylobacter?
Guillan Barre syndrome
How is culture done to determine if an infectious organism is present?
Growing culture in a variety of media and incubation conditions and takes 3 days to complete all tests
What are characteristics of salmonella gastroenteritis?
Symptom onset within 48 hours of exposure
Diarrhoea lasts less than 10 days
Around 5% of cases have positive blood cultures
Many patients still have positive stools at 20 weeks
What is associated with prolonged carriage of salmonella?
Gallstones
What are the 2 main species in the salmonella genus?
S.enterica
S.bongori
How is salmonella screened in the lab?
It is a lactose non-fermenter
How is E.coli O157 spread?
Contaminated meat or person to person spread
Why do blood cultures come up negative with E.coli O157 even with symptoms of sepsis?
The organism stays in the gut - its toxin gets into the blood
What is a major complication of E.coli O157 toxin being in the blood?
It can lead to Haemolytic uraemic syndrome
What is Haemolytic Uraemic Syndrome (HUS)?
Haemolytic anaemia and renal failure
Why are antibiotics contraindicated with E.coli O157?
Because they cause the organism to lysis and release greatly higher quantities of toxin
What are common bacteria that cause infectious diarrhoea?
Campylobacter
Salmonella
E.coli O157
Shigella
What patients with infectious diarrhoea should receive antibiotics?
Immunocompromised
Severe sepsis
Patients with chronic illness
How do C.difficile diarrhoea cases typically present?
History of previous antibiotic treatment
Severity ranges from mild to severe
How is C.difficile treated?
Metronidazole
Oral vancomycin
Fidaxomicin
Stool transplant
Why is vancomycin taken orally for C.difficile but IV for almost everything else?
It is very poorly absorbed, meaning it stays in the gut and has little systemic effect but a great effect on the C.difficle
How can C.difficile infection be prevented?
Reduce broad spectrum antibiotic prescribing
Isolate symptomatic patients
Wash hands with soap between patients
Cleaning environment
What are the 4Cs of antibiotics that increase C.difficile risk?
Cephalosporins
Co-amoxiclav
Clindamycin
Ciprofloxacin
How are protozoa infections diagnosed?
Microscopy - Parasites, cysts, and ova
What are symptoms of giardia duodenalis infection?
Diarrhoea
Gas
Malabsorption
Failure to thrive
How is Giardia duodenalis infection treated?
Metronidazole
What are symptoms of cryptosporidium parvum?
Diarrhoea
Nausea and vomiting
Abdo pain
How is viral diarrhoea diagnosed?
Antigen detection in stool
Where is norovirus commonly picked up?
Hospitals
Schools
Care homes
Cruise ships
How is norovirus diagnosed?
PCR
