Infectious diarrhoea Flashcards
Define diarrhoea
subjective description of frequent stools predominantly made up of fluid
Define Gastro-enteritis
3 or more loose stools per day with accompanying features (objective)
Define dysentery
obvious large bowel inflammation, bloody stools
How many types of stool are described in the Bristol stool chart?
7
type 1 - separate hard lumps type 2 - lumpy and sausage shaped type 3 - sausage but with cracks on surface type 4 - smooth sausage type 5 - soft blobs type 6 - fluffy pieces, mushy stool type 7 - watery, entirely liquid
Describe the epidemiology of Gastro-enteritis (how people can acquire it)
Contamination of foodstuffs (eg chicken and campylobacter)
Poor storage of produce (eg bacterial proliferation at room temp)
Travel-related infections (eg salmonella)
Person to person spread (eg norovirus)
Viruses are commonest cause and campylobacter is commonest bacterial pathogen
some trends in food poisoning?
Campylobacter - most common FOODBORNE pathogen
Salmonella - causes most HOSPITAL ADMISSIONS
Poultry meat linked to most causes of food poisoning
Defences against enteric infections
Hygiene
Stomach acidity (affected by antacids and infection)
Normal flora (affected by C. Diff diarrhoea)
Immunity (affected by HIV - salmonella)
Clinical features of diarrhoeal illness?
Non-inflammatory/secretory (eg cholera)
Inflammatory (eg shigella dysentery)
Mixed picture (eg C. diff)
features of non-inflammatory diarrhoeal illness?
secretory toxin mediated
- cholera: increases cAMP levels and Cl secretion, leading to water and sodium to also be secreted
- enterotoxigenic E. coli (travellers diarrhoea)
frequent watery stools with little abdo pain
rehydration mainstay of therapy
features of inflammatory diarrhoeal illness?
inflammatory toxin damage and mucosal (pain and fever)
bacterial infection/amoebic dysentery
antimicrobials may be appropiate but rehydration alone insufficient
what parts of the presenting complaint may be particularly relevant in assessing the patient?
- symptoms and their duration (over 2wks unlikely to be infective gastro-enteritis)
- Risks of food poisoning (dietary, contact, family history)
- Assess hydration (postural BP, skin turgor, pulse)
- features of inflammation: SIRS (fever, raised WCC)
- child features (sunken eyes+cheeks/decreased skin turgor/few or no tears when crying/dry mouth+tongue/sunken fontanelle)
what are the implications of fluid and electrolyte losses (more serious with secretory diarrhoea)
- 1 to 7L fluid per day lost containing 80-100mmol Na
- Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
- Hypokalaemia due to K loss in stool
what general investigations would you carry out on a patient presenting with diarrhoea?
- stool culture
- blood culture
- renal function
- blood count - neutrophilia, haemolysis
- abdominal x-ray if abdomen distended and tender
differential diagnosis of a patient with diarrhoea?
- IBD
- Spurious diarrhoea (secondary to constipation)
- Carcinoma
- diarrhoea and fever can occur with sepsis outside the gut (patient may have lack of abdo pain and tenderness which goes against gastroenteritis. Also likely to be no blood or mucus in stools)
treatment of gastro-enteritis?
Rehydration with
- oral rehydration with salt/sugar solution (
- iv saline
nb : note that the solution is given orally, must be given with sugar and amino acids as the uptake mechanisms are coupled with these
Describe key features of campylobacter gastroenteritis?
- Up to 7 days incubation so dietary history may be unreliable
- Stools negative within 6 weeks
- abdominal pain can be severe, rarely invasive
- post infection sequelae (GBS, reactive arthritis)
Discuss bacterial culture of campylobacter?
- commonest cause of bacterial food poisoning in UK
- C. jejuni/c. coli
- chickens, contaminated milk, puppies
- isolated cases not outbreaks
Discuss salmonella gastroenteritis and the routine bacterial culture for it?
- symptom onset usually within 2 days of exposure, diarrhoea lasts <10d
- 20% patients still have positive stools at 20/52 (associated with gallstones)
- screened put as lactose non-fermenters then antigen and biochemical tests
- genetically most are serotypes of same species (salmonella enterica)
What common salmonella isolates cause:
- gastroenteritis
- enteric fever
- Salmonella enteridis and typhimurium
- Salmonella typhi and paratyphi
What bacteria is associated with the following:
- infection from contaminated meat or person-to-person spread
- characteristic frequent bloody stools
- verocyto-toxin production by the bacteria in the gut, the toxin then gets into blood
- toxin can cause Haemolytic-uraemic syndrome (HUS)
E.coli O157 infection
Describe the patho-physiology of HUS and then classic signs and symptoms, and treatment?
patho-physiology
- toxin binds to globotriaosylceramide
- platelet activation stimulated
- micro-angiopathy results
- attach to endothelial, glomerular, tubule and mesangial cells
signs and symptoms
- renal failure
- haemolytic anaemia
- thrombocytopenia
treatment
-supportive (no antibiotics)
name some other bacteria associated with food poisoning outbreaks and what they are associated with?
> Shigella (4 species) - outbreaks of shigella sonnei in nurseries
enteropathogenic/enterotoxic(travellers diarrhoea)/enteroinvasive E.coli HOWEVER only O157 is easily diagnosed
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (toxin)
When should antibiotics be given in gastroenteritis (and when shouldnt you give antibiotics)?
indicated
- immunocompromised
- severe sepsis or invasive infection
- valvular heart disease
- chronic illness
- diabetes
contraindicated
-healthy patient with non-invasive infection
Discuss the severity and the toxins produced in C. Diff infection?
Severity ranges from mild diarrhoea to severe colitis
Enterotoxin (A) and cytotoxin (B) which is inflammatory
