Gastroenteritis
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  • 1. Gastroenteritis
  • 2.
    • Most common cause of significant adult gastroenteritis world-wide is bacterial infection.
    • Organisms to be discussed:
    • Salmonella
    • Campylobacter jejuni
    • Shigella
    • EHEC
    • Vibrio
    • Yersinia
    • Staph aureus
    • Bacillus cereus
    • Clostridium.
  • 3. Mechanisms
  • 4.  
  • 5. Salmonella
    • S. enteritidis and S. typhimurium .
    • Commensals in poultry and chicken.
    • Transmitted via contaminated foodstuffs and water.
    • Affects large and small bowel.
    • Typical symptoms starts between 12–48 hours after infection.
    • Spontaneous resolution usually occurs in 3–6 days.
    • Young children and elderly at risk of significant dehydration.
    • Treat with ciprofloxacin 500mg po bd reduced duration and severity of symptoms.
  • 6. Enteric Fever
    • Occur world-wide mainly in India and Africa.
    • Typhoid by Salmonella typhi.
    • Parathyphoid by S. paratyphi A, B or C.
    • Incubation period is 10–14 days.
  • 7. Clinical features
    • Invades small bowel (peyer’s patches) to regional LN to blood.
    • In early stages include:
    • Abdominal tenderness
    • Hepatosplenomegaly
    • Lymphadenopathy
    • Scanty maculopapular rash (‘rose spots’).
  • 8. Complications
    • (Usually in 3 rd week of illness)
    • meningitis
    • lobar pneumonia
    • osteomyelitis
    • intestinal perforation
    • intestinal haemorrhage
    • After clinical recovery they become convalescent carriers.
    • Usual site of carriage is the gall bladder
  • 9. Diagnosis
    • Culture of S. typhi or S. paratyphi from the patient.
    • Blood culture is positive in most cases in the first 2 weeks.
    • Bone marrow culture is more sensitive than blood culture, but is rarely required.
  • 10. Management
    • Ciprofloxacin 500 mg twice daily) are now the treatment of choice.
    • Azithromycin if resistant.
  • 11. Campylobacter jejuni
    • A common cause of childhood gastroenteritis in developing countries.
    • Affects small and large bowel.
    • Incubation period 2-4 days.
    • Self limiting in 3-5 days.
    • If severe treat with azithromycin 500mg po od.
  • 12. Shigella
    • Causes classical bacillary dysentery .
    • S. dysenteriae, S. flexneri and S. sonnei.
    • Only small numbers needed to be ingested to cause illness (<200).
    • Symptoms start 24–48 hours after ingestion
    • Frequent small-volume stools containing blood and mucus.
    • Self-limiting in 7–10 days.
    • Resistance to antibiotics is widespread.
  • 13. Entero haemorrhagic Escherichia coli (EHEC)
    • Also known as VTEC.
    • Secretes a toxin ( Shiga-like toxin 1 ) which affects vascular endothelial cells in the gut and in the kidney.
    • Incubation period of 12–48 hours.
    • Patient may develop TTP or HUS .
    • Treatment Is supportive.
    • Avoid antibiotics as may precipitate HUS.
  • 14. Vibrio
    • Vibrio cholera-next slide.
    • Vibrio parahaemolyticus causes acute watery diarrhoea after eating raw fish or shellfish that has been kept for several hours without refrigeration.
    • Self limiting up to 10 days.
  • 15. Cholera
    • Pure enterotoxigenic diarrhoea .
    • Gram-negative bacillus, Vibrio cholerae .
    • Common in Bangladesh, India and South East Asia.
    • Transmission is by the faeco-oral route
    • Proliferates in the small intestine .
    • Releases exotoxin which produces massive secretion of isotonic fluid into the intestinal lumen.
    • Releases serotonin (5-HT) from enterochromaffin cells in the gut, which activates a neural secretory reflex in the enteric nervous system.
  • 16.
    • Incubation period few hours to 6 days.
    • Majority have mild illness.
    • In severe cases:
    • profuse painless diarrhoea
    • ‘ rice water’ stool.
    • vomiting
    • hypovolemic shock.
    • Children may present with convulsions owing to hypoglycaemia.
    • Diagnosis is largely clinical.
    • Demonstration of organism in stool not diagnostic .
    • Stool and rectal swabs should be taken for culture to confirm the diagnosis.
  • 17. Treatment
    • Mainstay of treatment is rehydration.
    • Tetracycline or erythromycin x 3/7.
    • Help to eradicate infection, decrease stool output, and shorten the duration of the illness.
    • However, a single dose of ciprofloxacin or azithromycin (each 1 g) is a better choice.
    • Prevention by good hygiene and improved sanitation.
  • 18. Yersinia
    • Yersinia enterocolitica.
    • Human disease arise either via contaminated food products,ie: pork, or direct animal contact.
    • Watery diarrhoea, dysentery and mesenteric adenitis.
    • Self-limiting but ciprofloxacin may shorten the duration.
    • Y. pseudotuberculosis causes mesenteric adenitis and terminal ileitis .
  • 19. Staphylococcus aureus
    • Produce a heat-stable toxin ( enterotoxin B ) which causes massive secretion of fluid into the intestinal lumen.
    • Onset of symptoms is rapid , often within 2–4 hours of consumption.
    • Causes violent vomiting, followed within hours by profuse watery diarrhoea.
    • Symptoms have usually subsided within 24 hours.
  • 20. Bacillus cereus
    • Produces two toxins.
    • One causes diarrhea the other causes severe vomiting.
    • ‘ fried rice poisoning’
  • 21. Clostridial infections
    • Clostridium difficile causes antibiotic-associated diarrhoea, colitis and pseudomembranous colitis.
    • Gram-positive,anaerobic, spore-forming bacillus.
    • Normal flora in 3-5% general population.
    • Up to 20% in hospitalized patients.
    • Produces 2 toxins:
    • Toxin A (enterotoxin)
    • Toxin B (cytotoxic)
    • Almost all antibiotics have been implicated but the present increase has been attributed to the overuse of quinolones (e.g. ciprofloxacin ).
  • 22. Clinical features
    • Diarrhoea can begin anything from 2 days to a month after taking antibiotics.
    • The colonic mucosa is inflamed and ulcerated and can be covered by an adherent membrane-like material (pseudomembranous colitis).
  • 23. Diagnosis
    • Detecting A or B toxins in the stools by ELISA techniques.
  • 24. Treatment
    • Discontinue causative antibiotic.
    • Treat with metronidazole 400 mg po tds or
    • Oral vancomycin 125 mg po QID.
    • Isolation of patients with C. difficile.
  • 25.
    • Clostridium perfringens infection is due to inadequately cooked food .
    • Releases enterotoxin causing watery diarrhoea with severe abdominal pain, usually without vomiting.
  • 26. Travellers Diarrhea
  • 27.  
  • 28.  
  • 29. Possible questions
    • By which mechanism does vibrio cholera cause gastroenteritis?
    • Name 3 organisms causing watery diarrhea and profuse vomiting.
    • Clinical features of thyphoid fever.
    • In thyphoid, when does complications develop?
    • Common site for carriage of s.thyphi?
  • 30.
    • What is the most common cause of childhood gastroenteritis in developing countries.
    • A person had only eaten very small amount of food at a stall, becomes unwell with diarrhea. Passing frequent small-volume stools containing blood and mucus. Most likely organism?
    • Consequence of infection from EHEC?
    • Which toxin does EHEC secrete?
  • 31.
    • A person becomes very unwell with profuse painless diarrhoea, ‘ rice water’ stool , vomiting and ended up in ICU with hypovolemic shock. Most likely organism?
    • Which organism has the potential to cause mesenteric adenitis?
    • A person becomes unwell with vomiting and diarrhea only after several hours of eating dinner. Most likely organism?
    • A person eats fried rice takeaway and becomes sick afterwards. Most likely organism?
  • 32.
    • A person took ciprofloxacin a month ago and now develops diarrhea. Most likely organism? Treatment choice?
    • What is the most common organism in Traveller’s diarrhea?