Infectious Diarrhoea Flashcards
Definition of diarrhoea, gastro, dysentery
diarrhoea = subjective: fluidity and frequency
Gastro-enteritis: >/ 3 loose stools/day, accompanying features
Dysentery: obvious large bowel inflammation, bloody stools
Bristol Stool Chart
1: separate hard lumps like nuts, hard to pass
2: sausage shaped but lumpy
3: like a sausage but with cracks on surface
4: like a sausage/snake, smooth and soft
5: soft blobs with clear cut edges
6: fluffy pieces with ragged edges, mushy stool
7: watery, no solid pieces
Gastroenteritis cause
the contamination of foodstuffs - chicken and campylobacter
often due to poor storage - bacteria proliferate
Pathogenic causes of Gastroenteritis
Viral - are the most common cause (norovirus/rotavirus)
Bacterial. Campylobacter = most common bacterial pathogen.Salmonella = most common pathogen that causes hospital admission
Parasitic
Example of non-inflammatory/secretory diarrhoea
Cholera: is secretory toxin mediated. increases cAMP levels and Cl secretion. E.coli (travellers diarrhoea) is the most common cause. Water flows into the lumen and leads to dehydration.
Caused by bacterium: Vinrio cholerae
Frequent water stools with little abdominal pain
Rehydration is the main therapy
Example of inflammatory diarrhoea
Shigella dysentery (Shigellosis): inflammatory toxin damage. spread via faeces. Often seen in schools and children.
can cause fever and pain
Rehydration alone can be sufficient treatment but sometimes antimicrobials needed.
Example of a mix of secretory and inflammatory diarrhoea
C. diff. Often seen in those treated with antibiotics. very infectious. Treat with antibiotics (vancomycin/metronidazole)
If diarrhoea symptoms have lasted more than 2 weeks what is it unlikely to be?
Gastro-enteritis
Important history questions (4)
Length: >2/52 then unlikely gastro
Exposure risks: diet, contact, travel
Hydration: postural, skin turgor, pulse. in babies: few tears, sunken fontanelle, dry mouth
Inflammation features: WCC, fever
Fluid and Electrolyte loss
this can be severe in secretory diarrhoea
Investigations for prolonged diarrhoea (5)
stool culture blood culture renal function blood count - neutrophillia, haemolysis Abdo XR if abdo distended/tender
Differentials of prolonged diarrhoea (4)
IBD
Spurious diarrhoea - secondary to constipation (overflow)
Carcinoma
Diarrhoea and fever can occur with sepsis outside the gut, lack of abdo pain/tenderness goes against gastro
Treatment of prolonged diarrhoea
Rehydration - oral- rehydration with salt/sugar solution
IV - saline
Campylobacter Gastro
Most common cause of food poisoning. usually isolated cases rather than outbreaks. Up to 7 days incubation therefore dietary history may be unreliable. Stools negative within 6 weeks. Severe abdo pain.
post infection sequelae: guillian-barre, reactive arthritis
Culture: Has specialised conditions. comes from chickens, contaminated milk, puppies.
TREAT: azithromycin
Salmonella Gastro
Symptoms usually onset <48 hourrs post exposure
Last less than 10 days
20% still have positive stools at 20 weeks - prolonged carriage may be associated with gallstones. post-infectious irritable bowel common.
Culture: screened out as lactose non-fermenters.
Salmonella enteritidis and typhimurium most common
Treatment: CIPROFLOXACIN
E.coli O157
infection from contaminated meat or person to person spread. typically characterised by frequent bloody stools. produces verocyto-toxin.
Stays in the gut but the toxin moves to the blood. toxin can cause haemolytic-uraemic syndrome (HUS) - haemolytic anaemia, renal failure and thrombocytopenia.
Treatment - supportive. ANTIBIOTICS NOT INDICATED
Other bacteria
shigella - nurseries etc
staph aureus
bacillus cereus - reheated rice
When should antibiotics be given (5)
immunocompromised severe sepsis/invasive infection valvular heard disease chronic illness diabetes
When should antibiotics not be given?
not indicated in healthy patient with non-invasive infection
C. diff
Produces spores
Usually a history of antibiotic treatment. severity ranges from diarrhoea to severe colitis.
O2 resistant, heat resistant, alcohol gel resistant
Produces toxins: enterotoxin A and cytotoxin B, c. diff transferase
Positive toxin test doesnt always mean disease - diarrhoea symptoms need to be present for diagnosis
4 Cs of antibiotics
Cephalosporins
Co-amoxiclav
Ciprofloxacin (and other quinolones)
Clindamycin
Treatment of C.diff
ORAL vancomycin metronidazole Fidaxomicin (new and expensive) Stool transplants May require surgery
C.diff prevention
reduction in antibiotic prescription
avoid 4 Cs
isolate symptomatic patients
wash hands WITH SOAP
Parasitology
order stool sample with PCO
