Gastroenteritis Flashcards
Risk factors
Age < 5, not breastfed Malnutrition (micronutrient) deficiency Exposure to contaminated food and water Winter congregation/summer floods Acid suppression, immunosuppression, microbiome, genetics
What is diarrhoea
> 3 unformed stools/day, liquid enough to hold shape of a container
How can diarrhoea be classified
Using the bristol stool chart
What is dysentry
Inflammation of intestine resulting in diarrhoea with blood and mucous. Can be due to Shigella or Campylobacter
Symptoms of dysentry
Diarrhoea with blood and mucous, fever, abdominal pain, rectal tenesmus
What is rectal tenesmus
Feeling of incomplete defaecation
Infection with what may mimic appendicitis
Yersinia enterocolitica as it may invade mesenteric nodes
What is gastroenteritis
Illness caused by eating food contaminated by micro-organisms, toxins, poisons, etc
What type of diarrhoea does Cholera cause
Of large bowel
History taking during gastroenteritis
Diarrhoea frequency, blood, mucous, time course
Travel history, human or animal contact
Food history (time, type, storage, reheating, washing)
Age, comorbodities, medication history
What is generally found in starchy food
Bacillus cereus, produces heat-resistant spores. Often found in leftover rice not heated enough causing profuse vomiting. Gram positive bacillus, incubation 1-6 hours
Pathogen found in milk/meat/fish
Staphylococcus aureus, gram positive coccus. Found in dairy products such as milk/meat/fish and food left at room temperature. Rapid absorption of preformed toxins that act on the vomit centre causing profuse vomiting and abdominal pain
Laboratory identification of pathogens
Traditional method - Less expensive, slower, more narrow and only live bugs grow.
Molecular methods - More expensive but faster. Broad range of bug but not sensitive as all the bugs present come up, not the causative agent
How long does a culture result take
48 hours
Most described Shigella species
S.dysenteriae
What toxic factors does Shigella produce that causes dysentry
Shiga toxins
What does Shiga toxin do
Bind to receptors on renal cells, RBC and others inhibiting protein synthesis. This causes cell death
Are Shiga toxins only produced by Shigella
No, other bacteria produce Shiga toxins
What were STEC previously known as
Shiga Toxin producing E.coli (STEC) was previously known as verotoxins
How can STEC cause haemolytic uraemic syndrome (HUS)
STEC compete with normal bowel flora and bind to enterocytes. This elaborates shiga-toxins which bind to absorptive enterocytes. This causes irreversible inhibition of protein synthesis resulting in death of enterocytes. These damage intestinal epithelium cells provide easy entry into bloodstream for Shiga-toxins where they cause death of endothelial cells. This activates clotting, platelet aggregation, cytokine secretion, vascular constriction and clot formation. Microangiopathy propagates distally as toxins are carried to the kidneys causing haemolysis (death of red cells) and uraemia (kidney failure).
Haemolytic and uraemic syndrome is mainly associated with what serotype
Serotypes that produce Shiga toxin 2
Administering antibiotics in an E.coli O157:H7 infection
Antibiotics in an E.coli O157:H7 can cause in increase in Shiga toxin production (especially STX2). This increases the risk of haemolytic uraemic syndrome (HUS) and can be fatal
What age groups is E.coli O157 infection most found
50% caes < 16 years old, < 5 is highest number of cases
How can E.coli O157 infection be passed on
Raw beef, milk, water, person to person direct contact with children and elderly more at risk
What pathogen can cause haemorrhagic colitis
E.coli O157:H7
What is EHEC also known as
Enterohaemorrhagic E.coli is also known as VTEC/STEC and E.coli O157
