Infectious diarrhoea Flashcards
List the bacteria that are sought by routine culture of stools from patients with diarrhoea in the UK and outline their epidemiology (6)
List other bacteria (4) that cause diarrhoea, indicate the availability of routine tests for them
Routine:
Salmonella (S. sonnei, S.flexneri, S.boydii, S. dysenteriae)
campylobacter,
E. coli O157,
shigella,
clostridium (C. perfringens, C. difficile)
cryptosporidium
Cholera
Other forms of E. coli (enterotoxigenic E. coli)
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
List the parasites commonly detected in stool specimens in the UK by microscopy
Giardia duodenalis (aka G. lamblia/G. instestinalis)
Cryptosporidium parvum
Entamoeba histolytica
List the viruses that commonly cause diarrhoea (3)
Rotavirus,
Norovirus,
Adenovirus (serotypes 40/41)
Define
- food-poisoning
- gastro-enteritis
- dysentery
- colitis.
Gastro-enterits
-3+ loose stools in 24hrs plus at least one of fever, vomiting, pain, blood/mucus stools
Dysentery
-large intestine inflammation, bloody stools
Commonest pathogenic cause of gastro-enteritis
Virus
Commonest bacterial cause of gastro-enteritis
Campylobacter
Host’s natural defences against enteric infections (6)
Age HYGIENE Stomach acidity Gut motility Normal gut flora Gut Immunity
Mechanisms of diarrhoea
toxin mediated, invasion, attachment
2 types of diarrhoea
Non-inflammatory/secretory:
- Toxin-mediated usually
- Watery stools, rapid dehydration, relatively little abdo pain
- Rehydration mainstay of treatment
Inflammatory:
- Bacterial infection usually
- Abdo pain, bloody stools, sytemic upset
- Rehydration and (sometimes) antimicrobials required
An example of non-inflammatory/secretory diarrhoea
Cholera
An example of inflammatory diarrhoea
Shigella
Mechanism of cholera in causing non-inflammatory diarrhoea
Cholera is TOXIN-MEDIATED
- toxin produced stimulates adenylate cyclase which subsequently increases cAMP levels results in loss of Cl- from intestinal epithelial cells along with Na+ and K+
- so creates big osmotic pressure that drags water out from gut cells INTO LUMEN
Mechanism of inflammatory diarrhoea, e.g. shigella
Bacterial infection causes mucosal destruction by inducing pro-inflammatory cytokine release; these cytokines attract immune cells to destruct the epithelium lining the gut mucosa
Taking the history of someone with diarrhoea
- what to ask about symptoms (4)
- risks (6)
duration of diarrhoea, frequency and consistency of stool, other symptoms
Risks - food, occupation, travel, antimicrobials, contacts, institution (i.e. hospital, school)
If diarrhoea symptom duration >2 weeks then diagnosis unlikely to be…
infective gastro-enteritis
Examination of hydration status in diarrhoeal patient
-what to examine
Pulse,
Postural BP
skin turgor (not great as you lose this as you age anyway)
Signs of gastro-enteritis in infant/child
Decreased skin turgor Sunken eyes and cheeks Sunken fontanelle Dry mouth/mucous membranes Sunken abdomen
General investigations of gastro-enteritis
Stool and blood culture, renal function, Full blood count - looking for neutrOphilia, haemolysis (indicates E. coli O157) sigmoidoscopy, Abdo X-Ray, serology
Differential diagnosis of gastro-enteritis
IBD
Sepsis - diarrhoea as response to sepsis
General treatment of gastro-enteritis
Rehydration therapy - salt/glucose solution or IV saline
Fasting?
Anitbiotics?
Treat complications
Occasional causes of food poisoning outbreaks
Staph aureus (toxin) Bacillus cereus (re-fried rice) Clostridium perfringens (undercooked meat/cooked food left out - toxin accumulates in spore formation)
Antibiotics only indicated in gastro-enteritis if
immunocompromised
severe sepsis or invasive infection (i.e. not localised to gut anymore)
chronic illness e.g. malignancy
The 4 ‘C’ antibiotics that induce C. diff diarrhoea
cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin
Ways of preventing C. diff diarrhoea
- Reduce broad spectrum antibiotic use
- Avoid 4 Cs
- Wash hands with SOAP + WATER (spores are resistant to alcohol gel)
- Clean environment on discharge
