My Gastrointestinal infections

Card Set Information

My Gastrointestinal infections
2012-01-03 13:42:10
GI infection

Questions on common GI infections
Show Answers:

  1. Outline how a consumed pathogen can cause disease
    • Intoxication: The toxin of an organism is ingested, with or without the live organism
    • Infection: Disease is due to microbe ingestion, which colonise the GI tract any may invade
  2. What are the criteria for diarrhoea? What is its significance?
    • Abnormal frequeny and/or fluidity of stool (~3+ daily)
    • Usually indicates small bowel disease
    • Causes fluid and electrolyte loss
    • Severity can vary from self limiting to fatal, depending on pathogen's virulence and host's immunity
  3. What is dysentery? What are its clinical features?
    • An inflammatory disorder of the large bowel, causing blood and pus in the faeces
    • Pain, fever and abdominal cramps
  4. What aspects of a clinical history should be explored when suspecting a IID?
    • Vomiting or diarrhoea? Any blood?
    • Abdominal pain?
    • Frequency/nature of symptoms
    • Onset speed
    • Travel/food/contact history (e.g. ill friend or recent BBQ)
  5. Outline the methods used to diagnose a suspected IID
    • History: Discussed in another question
    • Examination: Abdominal features/fever/dehydration
    • Laboratory: Cultures
  6. What different media can be used to minimise culture contamination by normal GI flora?
    • Enrichment: Media beneficial to the suspected pathogen
    • Selective: Media suppresses normal flora
    • Differential: Media has a chemical affected by a suspected pathogen's biochemical processes, causing colour change (e.g. non-lactose fermenters or haemolytic strep
  7. Outline the common treatment of bacterial IIDs
    • Majority of mild bacterial GI infections will resolve spontaneously
    • Adequate hydration important, especially when V/D
    • Antibiotics reserved for severe/prolonged disease, as they may prolong or exacerbate disease and cause resistance
  8. What bacteria shows in microscopy as curved bacilli?
  9. Transmitted by contaminated food, milk or water
    Seasonal peaks in May and September
    Especially found in poultry
  10. What is the pathogenesis of campylobacter?
    • Invasion in small and large bowel
    • Causes inflammation, ulceration and bleeding
    • Bacteraemia can occur by dissemination, usually only in immunocompromised
  11. Patient presents with:
    - Bloody diarrhoea
    - Cramping abdominal pain
    - Fever
    - Lasts up to 3 weeks
  12. How is campylobacter treated?
    • IV fluids
    • If severe/persistent disease, clarithromycin
    • If invasive, quinolone or aminoglycosides
  13. List the common gram negative IIDs
    • Campylobacter
    • H.Pylori
    • E.Coli
    • Salmonella
    • Shigella
    • Vibrio cholerae
    • Yersinia entercolitica
    • CHESS VY
  14. List the common gram positive IIDs
    • Bacillus
    • Listeria
    • Aureus
    • Clostridium
    • BLAC
  15. How is salmonella spread? What is its pathogenesis?
    • Large animal reservoir creates contaminated food, causing outbreaks. Also waterbourne or sometimes horizontal
    • Epithelial invasion of distal small intestine = inflammation. Bacteraemia in immunocompromised.
  16. Patient presents with:
    - Watery diarrhoea
    - Vomiting
    - Fever in later stages.
    - Lasts 2-7 days
  17. How is salmonella treated?
    • IV fluids
    • Antibiotics used in invasive/metastatic infections
    • Beta lactams, quinolones and aminoglycosides used
  18. How is shigella transmitted?
    • Humans the only reservoir of S.Dysenteriae; spread by faecal-oral.
    • Low infectious dose
    • Does not persist in the environment or in food.
  19. What is the pathophysiology of shigella?
    • Organisms colonises mucosal epithelium of terminal ileum and colon
    • Exotoxin produced = epithelial damage and renal failure (haemolytic uraemic syndrome)
  20. Patient presents with :
    - Watery diarrhoea which becomes bloody.
    - Marked cramping abdominal pain
    - Fever
    - Lasts 2-3 days
  21. How is shigella treated?
    • IV fluids
    • In H-U syndrome or in the infirm, 3rd generation cephalosporins are used.
  22. What bacteria shows up in microscopy as comma shaped bacilli?
    Vibrio cholerae
  23. How is V.Cholerae transmitted?
    • Persists in fresh water, spread by sewage contamination of food/water
    • Human-only faecal-oral spread
  24. What is the pathophysiology of V.Cholerae?
    • Flagellae and mucinase used to penetrate intestinal mucous
    • Attaches to receptors
    • Exotoxin production causes increased electrolyte and fluid loss
    • Hypokalaemia, metabolic acidosis (from hyperchloraemia), hypovolaemia and cardiac failure
  25. Patient presents with frequent, profuse, non-bloody, watery diarrhoea.
    • Vibrio Cholerae
    • Diarrhoeal bacillus cereus (with cramping pain)
  26. How is V.Cholerae treated?
    • Immediate oral or IV rehydration
    • Tetracyclines can shorten shedding duration, but little effect on severity.
  27. Describe EPEC
    - Aetiology
    - Pathophysiology
    - Clinical features
    • Found in infants/children and travellers
    • Adherence causes a lesion, disrupting microvilli of intestine = electrolyte loss
    • Watery diarrhoea, abdominal pain, vomiting and fever
  28. Describe ETEC
    - Aetiology
    - Pathophysiology
    - Clinical features
    • Infants/children. Major cause of travellers diarrhoea
    • Plasmid toxins released
    • Watery diarrhoea, abdominal pain and vomiting. No fever
  29. Describe EHEC
    - Aetiology
    - Pathophysiology
    - Clinical features
    • Worldwide outbreaks. Contaminated food, water, dairy or faecal oral
    • EPEC-lesion, but also shiga-like toxins released
    • Bloody diarrhoea, abdominal pain, vomiting, no fever. HUS = thrombocytopenia, renal failure, anaemia
  30. Describe EIEC
    - Aetiology
    - Pathophysiology
    - Clinical features
    • Poor hygeine/sanitation. Also foodbourne
    • Endocytosis into large intestine mucosa = cell lysis = inflammation, necrosis and ulceration
    • Bloody diarrhoea, cramping, vomiting, fever
  31. What bacteria is the cause of 'fried rice syndrome'? Explain this name and list its clinical features
    • "Emetic" bacillus cereus
    • Bacteria spores persist through initial boiling, then rice left to cool. Spores germinate, multiply and produce heat-stable toxin. After frying, consumption causes near immediate illness.
    • Profuse vomiting, abdominal cramps, watery diarrhoea.
  32. Outline the transmission and clinical features of listeria monocytogenes
    • Associated with contaminated foods, especially unpasteurised dairy, pate, cooked meats, smoked fish. Can multiply at 4 celcius
    • 3 week incubation, with flu like symptoms usually ignored and so clinically presents as severe systemic infection (e.g. septicaemia or meningitis)
  33. What is the treatment for an H. Pylori infection?
    • Proton pump inhibitor
    • Clarithromycin
    • Amoxicillin (or Metronidazole in hypersensitive)
  34. Outline the pathophysiology of a staph aureus GI infection
    • 50% of strains produce an exotoxin; acid resistant and heat stable.
    • Bacteria multiply and produce toxin at room temperature
    • Incubation period from 15 mins to 6 hours
  35. What virus is the commonest cause of life-threatening diarrhoea in young babies?
  36. Child presents with viral gastroenteritis, with worse vomiting and diarrhoea than expected. Recent history of outbreak in family/daycare
  37. Child presents with cervical lymphadenopathy, watery diarrhoea and fever/vomiting
    Respiratory type adenovirus
  38. What is the most common cause of non-bacterial gastroenteritis?
  39. What virus normally reappears yearly? When does the outbreak normally occur?
    • Norovirus
    • January, but also September-November