Infectious diarrhoea Flashcards
Define diarrhoea
subjective description of frequent stools predominantly made up of fluid
Define Gastro-enteritis
Describe 5 accompanying features
3 or more loose stools per day with accompanying features (objective) Fever Bloody stools Mucus in stools Vomiting Pain
Define dysentery [2]
obvious large bowel inflammation, bloody stools
How many types of stool are described in the Bristol stool chart?
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 transmission of Gastro-enteritis (how people can acquire it) [4]
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)
5 Defences against enteric infections
Hygiene
Stomach acidity (affected by antacids and infection)
Normal flora (affected by C. Diff diarrhoea)
Immunity (affected by HIV - salmonella)
Types of diarrhoeal illness [3]
Non-inflammatory/secretory (eg cholera, traveler’s diarrhea)
Inflammatory (eg shigella dysentery)
Mixed picture (eg C. diff)
Features of non-inflammatory diarrhoeal illness? [2]
Mx [1]
secretory toxin mediated
frequent watery stools with little abdo pain
rehydration mainstay of therapy
2 types of inflammatory diarrhoeal illness?
Mx [1]
inflammatory toxin damage and mucosal destruction (pain and fever)
bacterial infection/amoebic dysentery
Management:
antimicrobials may be appropiate but rehydration alone insufficient
what parts of the presenting complaint may be particularly relevant in assessing the patient? [4]
- symptoms and their duration (over 2wks unlikely to be infective gastro-enteritis)
- Likelihood of food poisoning (dietary, contact, family history)
- Assess hydration (postural BP, skin turgor, pulse)
- Features of inflammation: SIRS (fever, raised WCC)
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? [5]
- stool culture & microscopy for ova, cysts and parasites
- blood culture (positive in salmonella)
- renal function (AKI)
- blood count - neutrophilia, haemolysis
- abdominal x-ray (perforation)
Differential diagnosis of a patient with diarrhoea? [4]
- IBD
- Spurious diarrhoea (secondary to constipation)
- Carcinoma
- Sepsis outside gut
Treatment of gastro-enteritis? [2]
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
Campylobacter gastroenteritis Incubation period impacting history and dx Investigations Presenting complaint Post-infection sequelae [2]
- Up to 7 days incubation so dietary history may be unreliable
- Stools negative within 6 weeks
- abdominal pain can be severe, rarely invasive (bacteremia)
- post infection sequelae (GBS, reactive arthritis)
Discuss bacterial culture of campylobacter?
2 common strains
3 sources
Management
-C. jejuni/c. coli
- chickens, contaminated milk, puppies
Mx: ciprofloxacin
Discuss salmonella gastroenteritis and the routine bacterial culture for it? Onset, course Positive stools at... Risk factors Post-infection sequelae
- symptom onset usually within 2 days of exposure, diarrhoea lasts <10d
- 20% patients still have positive stools at 20/52 (associated with gallstones)
- screened out as lactose non-fermenters then antigen and biochemical tests
- genetically most are serotypes of same species (salmonella enterica)
Associated with reptile contact
Post-infection irritable bowel common
What common salmonella isolates cause:
- gastroenteritis
- enteric fever
- Salmonella enteridis and typhimurium
- Salmonella typhi and paratyphi
E.coli O157 infection features: Route of transmission Characteristic clinical feature Incubation period Pathogenesis [2] Complication
- infection from contaminated meat or person-to-person spread
- characteristic frequent bloody stools
- 24-48h
- verocyto-toxin or shiva-like toxin production by the bacteria in the gut, the toxin then gets into blood
- toxin can cause Haemolytic-uraemic syndrome (HUS)
Describe the patho-physiology of HUS: Onset Pathophysiology mechanism [4] SXS 3 Treatment: Supportive measures Prophylactic measures
5-7 days between onset of diarrhea and HUS
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 dialysis (no antibiotics)
- prophylactic
- plasma exchange
Name some other bacteria associated with food poisoning outbreaks and what they are associated with? [4]
> Shigella - outbreaks of shigella sonnei in nurseries
Staph aureus (toxin)
Bacillus cereus (re-fried rice)
Clostridium perfringens (toxin)
When should antibiotics be given in gastroenteritis (and when shouldnt you give antibiotics)? [5]
indicated
- immunocompromised
- severe sepsis or invasive infection
- valvular heart disease
- chronic illness
- diabetes
contraindicated
-healthy patient with non-invasive infection
How is parasitology (usually protozoa and helminths) diagnosed?
What specific request needs to be sent with stool sample?
Microscopy
Request PCO
What are the main UK parasites?
Presentation [3] in Giardia
Where must biopsy be taken to dx in Giardia?
Route of transmission in both
Treatment in both
Where are cysts seen - answer for both
Both same causative factor- contaminated water
Giardia Lamblia
- Diarrhoea, malabsorption and failure to thrive
- Distal duodenal biopsy to diagnose.
- Cysts seen on stool microscopy
- Tx: metronidazole
Cryptosporidium parvum
- cysts seen on microscopy
- metronidazole
Discuss Entamoeba histolytica (example of imported parasite) Define in 2 words 2 types Long term complication Tx [2]
- amoebic dysentery
- vegetative form in symptomatic patient (hot stool)
- cysts seen in asymptomatic patient
- amoebic liver abscess may be long term complication (anchovy pus)
- treat symptomatic disease with 10w metronidazole, fur amide for cyst carriage
What virus is known to cause diarrhoea in children under 5 yrs? Route of transmission Dx Pathophysiology [2] Mx
Rotavirus Fecal-oral route Antigen detection Infects mature enterocytes of vilous body and tip > cell death and lactose intolerance Mx: supportive
Discuss Norovirus:
- where does it tend to cause outbreaks?
- diagnosis
- protocol for management
- incubation period
- Route of transmission [2]
- tends to cause outbreaks in hospitals, cruise ships. Very infectious
- PCR to diagnose
- strict infection control measures needed. Quarantine area etc
- incubation: 24-48 hours
- ROT: contact, aerosol
Pathogenesis of cholera [2]
Ab?
cholera: increases cAMP levels and Cl secretion, leading to water and sodium to also be secreted
Mx: Tetracycline
Pediatric features of dehydration [5]
- sunken eyes+cheeks
- decreased skin turgor/few or no tears when crying
- dry mouth+tongue
- sunken fontanelle
What strains of adenovirus can cause diarrhea
Adenovirus 40 and 41
One of differentials of diarrhea is sepsis outside gut - describe its presentation:
Lack of… [2]
2 classical features
Likely to be no… [2]
-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)
E Coli O157 management
Loperamide
Rehydration
Antibiotic if systemic signs: azithromycin
Management for cholera, salmonella, bacillus cereus
Cholera: ciprofloxacin
Salmonella: ciprofloxacin
Bacillus cereus: vancomycin only if immunocompromised
