Gi infections

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  • Inflammatory diarrhea
  • SA: n/v CNS, Botulinum on NMJ Enterotoxin: direct effect on intestinal mucosa to elicit net fluid secretion Cyto; mucosal destruction causing inflam colitis

Transcript

  • 1. Gastro-intestinal Infections Dr Kamran Afzal Classified Microbiologist
  • 2. Diarrhea
    • Symptoms Increase in stool frequency/ volume and/or decrease in consistency
    • Signs Stool water excretion more than 150-300 ml above normal
  • 3. Classification Of Diarrheas
    • Duration
      • acute
      • chronic
    • Affected organ
      • small intestine
      • large intestine
    • Clinical description
      • volume
      • frequency
      • consistency
      • presence of blood
    • Patho-physiologic
      • inflammatory
      • (infectious)
      • non-inflammatory
      • (non-infectious)
  • 4. 1. Non-inflammatory vs inflammatory
    • Noninflammatory diarrhea
      • Pathogens act primarily on small intestine to induce fluid secretions
      • Voluminous watery diarrhea, dehydration, nausea, vomiting, abdominal cramps, low grade fever
      • No blood, pus, tenesmus, or fever
      • No fecal leukocytes, and rarely occult blood
    • Inflammatory diarrhea
      • Induce inflammation by invasion or cytotoxins
      • Stools of small volume, fever, blood and mucus, tenesmus, abdominal cramping
      • Dehydration unusual
      • Fecal leukocytes, occult blood
  • 5. Infectious Diarrhea - Possible Pathogens
    • Bacteria
    • Invasive and Cytotoxin-producing Microorganisms Salmonella spp
    • Shigella spp
    • Campylobacter spp
    • Vibrio cholerae
    • Escherichia coli (EPEC, EHEC, ETEC, EIEC)
    • Clostridium difficile
    • Aeromonas hydrophila
    • Yersinia enterocolitica
    • Vibrio parahaemolyticus
    • Listeria monocytogenes
  • 6.
    • Bacteria (Food Poisoning-Enterotoxigenic) Staphylococcus aureus
    • Clostridium perfringens
    • Bacillus cereus
  • 7.
    • Protozoa Giardia lamblia Entamoeba histolytica Balantidium coli Isospora belli Cryptosporidium Microsporidium Cyclospora
    • Viruses
    • Rota virus
    • Enteric Adeno virus
    • Norwalk virus
    • Calici virus
    • Astro virus
  • 8. Infectious doses of enteric pathogens
    • Shigella 10 1-2
    • Giardia lamblia 10 1-2
    • Entamoeba histolytica 10 1-2
    • Campylobacter jejuni 10 2-6
    • Salmonella 10 5
    • E. coli 10 8
    • Vibrio cholerae 10 8
  • 9. Fecal leukocytes
    • Shigellosis
    • Enteroinvasive E. coli
    • Clostridium difficile
    • Salmonella enteritidis
    • Vibrio parahemolyticus
    • Ulcerative colitis
    • Ischemic colitis
  • 10. Pathophysiology
    • Toxin production
    • Entero-adherence
    • Mucosal invasion
    • Antibiotic associated colitis
  • 11. a. Toxin production
    • Neurotoxins (preformed toxin)
      • Bacillus cereus , Clostridium perfringens , Staphylococcus aureus
    • Enterotoxin
      • Intracellular mediators
        • Increased cyclic AMP, GMP or Calcium
      • Vibrio cholerae, Aeromonas species, ETEC
    • Cytotoxin
      • Destruction of the mucosal cells
      • Clostridium difficile, E. coli 0157:H7, Shigellae
  • 12. b. Entero-adherence
    • Pili or fimbirae bind to specific receptors
      • Enteroadherent and enteropathogenic E. coli
      • Giardiasis ( Giardia lamblia )
      • Helminths
      • Cryptosporidiosis ( Cryptosporidium parvum)
      • Cyclospora species (?)
  • 13. c. Mucosal invasion
    • Minimal invasion
      • Norwalk virus, Rotavirus, other viruses
    • Variable invasion
      • Aeromonas sp., Campylobacter sp., Salmonella sp., Vibrio parahemolyticus
    • Severe invasion
      • Intense inflammatory response
      • Entamoeba histolytica , enteroinvasive E. coli , Salmonella and Shigella species
  • 14. d. Antibiotic Associated Colitis
    • Antibiotic exposure
    • Intestinal endogenous flora
    • Exposure to C. difficile in environment
    • Colonic colonization - C. difficile
    • Elaboration of toxin(s)
    • Diarrhea and colitis
  • 15. Features Of Food Poisoning Agents ++ + +++ 8-72 hrs 8-24 hrs Cl. perfringens ++ +++ + 2-10 hrs 1-6 hrs Bacillus cereus ++ +++ + 12-24 hrs 1-8 hrs Staph aureus Enterotoxin Vomiting Diarrhea Duration Incubation period Organism
  • 16. Salmonella gastroenteritis
    • S. typhi is confined to humans so spread is purely faecal-oral
    • Non-typhoidal strains such as ( S. enterica ) serovars S. typhimurium, S. enteritidis, etc
    • Found in GI tracts of mammals, birds, reptiles
    • Acquired from ingestion of contaminated poultry, eggs, meat and exposure to pet reptiles
    • Fever, abdominal cramping, nausea, vomiting, diarrhea with fecal leukocytes
    • Untreated diarrhea lasts 4-10 days
  • 17. Shigellosis
    • Four species:
      • S. dysenteriae, S. flexneri, S. boydi, S. sonnei
    • Highly infectious: infectious dose < 200
    • Incubation period 1-7 days
    • Symptoms can develop 12 hours after ingestion
    • Presents as fever, abdominal pain, tenesmus, bloody diarrhea
    • Anti-motility drugs have been associated with toxic megacolon
    • Self-limited but treatment recommended to prevent secondary spread to contacts
  • 18. E. coli gastroenteritis
    • Enterohemorrhagic ( E coli 0157:H7)
      • Most common strain in developed countries
      • Usually transmitted by beef, but many other foods
      • Low infectious dose (as few as 100 bacteria)
      • Shiga-toxin
      • Crampy abdominal pain
      • Copious bloody diarrhea sometimes with the hemolytic-uremic syndrome
  • 19.
    • Enterotoxigenic
      • Most common cause of travelers diarrhea
      • Acquired by ingestion of fecally contaminated food or water
      • Occurs 3-14 days after ingestion
      • Causes watery diarrhea, abdominal cramps occasionally nausea and vomiting
      • Self-limiting lasts 1-5 days
  • 20.
    • Enteropathogenic
      • Diarrhea in infants common in developing countries
    • Enteroinvasive
      • Dysentery with blood and mucus
    • Enteroaggregative
      • Dysentery with blood and mucus
  • 21. Transmission of E. coli O157
    • Raw milk
    • “ Pasteurised milk”
    • Yoghurt
    • Cheese
    • Cream
    • Vegetables
    • Salad vegetables
    • Mayonnaise
    • Apple cider (USA)
    • Fruit
  • 22. Vibrio cholerae
    • 01 serotype: (Cholera) watery diarrhea, dehydration; associated with residence in endemic areas, Toxin causes host cells to secrete Cl – , HCO – , and water
    • Non-01-serotypes: (Noncholera vibrios) diarrhea, fever, nausea, vomiting, blood in stool; often associated with traveler’s diarrhea
      • V. parahaemolyticus
      • V. vulnificus
  • 23. Staphylococcal food poisoning
    • Common food borne illness
    • Infections originate from asymptomatic carriers of Staphylococcus aureus
    • Can contaminate processed meats, salad, ice-cream
    • Preformed toxin (enterotoxin) in food rather than from direct effect of organism
    • Incubation period about 4 hours
    • Symptoms last < 24 hours
      • No new toxin produced by ingested bacteria
    • Severe nausea and vomiting along with abdominal pain and diarrhea
    • No fever
  • 24. Traveler’s diarrhea
    • Bacterial
      • Enterotoxigenic E. coli (ETEC)
      • Shigella
      • Salmonella
      • Campylobacter
    • Protozoa
      • Giardia, Entamoeba, Cryptosporidium
    • Virus
      • Norwalk, rotavirus, enterovirus
  • 25. Helicobacter pylori
    • 70-90% of population in developing countries
    • Associated with gastritis, duodenal ulcer, gastric ulcer and gastric adenocarcinoma
    • Fecal-oral transmission
  • 26. Intestinal tuberculosis
    • Primary – ingestion of organism in unsensitised host
    • Can cause severe ulcero-inflammatory disease with perforation
    • Secondary – swallowing of infected sputum
    • Most common in terminal ileum and jejunum
    • Complications – obstruction, fistula
  • 27. Clostridium difficile
    • 1970s: Found to be the cause of enterocolitis related to the antibiotic clindamycin
    • Pseudomembranous colitis with yellow-white plaques; can progress to toxic megacolon
    • At least two toxins (A and B) cause necrosis of epithelium
    • Nosocomial transmission
    • Widespread contamination of hospital environments
  • 28. Endoscopic view of multiple scattered, yellowish plaques consistent with pseudomembranous colitis
  • 29. Abdominal radiograph demonstrating markedly dilated colon, wall edema, and loss of haustrations in a patient with Clostridium difficile- associated pseudomembranous colitis complicated by toxic megacolon
  • 30. Entamoeba histolytica (amebiasis)
    • Affects 10% of world’s population
    • Order of involvement: caecum, ascending colon, rectum, sigmoid
    • Flask-shaped ulcers
    • Liver abscesses in up to 10%
  • 31. Giardia lamblia (giardiasis)
    • Waterborne
    • Can cause diarrhea by several mechanisms
    • Weight loss, cramps, steatorrhea, flatulence, vomiting, belching, fever
  • 32. Rotavirus diarrhea
    • Usually sporadic but can cause epidemics in institutions, including nursing homes
    • Cytopathic effect on mature enterocytes, replaced by immature cells with loss of absorptive function
      • Usually infants and young children
    • Fecal-oral transmission
  • 33. Norovirus diarrhea
    • Typically epidemic, often traced to a common source
    • Throughout the year
    • Often traced to contaminated food or water
      • Usually adults and school-aged children
  • 34. HIV associated diarrhea
    • Diarrhoea is a big problem
    • Opportunistic infection
      • Candida, cryptosporidia, cytomegalovirus, Mycobacterium avium-intracellulare, strongyloides, leishmaniasis
    • HIV itself causes enteropathy
  • 35. Dysentery
    • Bacillary
    • High frequency
    • Blood and mucus
    • Not sticky
    • Alkaline
    • Pus cells > RBCs
    • Macrophages
    • Amoebic
    • Low frequency
    • Blood and mucus, mixed with stools
    • Sticky
    • Acidic
    • RBCs > Pus cells
    • Trophozoites of E. histolytica
  • 36. Diagnosis - Stool Collection and Transport
    • Appropriate container
    • Proper instructions to the patient
    • Representative portion of stool
    • Fresh specimen
    • Freshly collected rectal swab
    • Transport as early as possible
    • Use transport media – buffered glycerol saline or alkaline peptone water
  • 37. Diagnostic Evaluation
  • 38. Protocol For Specimen Processing
  • 39. Laboratory Diagnosis
    • Stool Microscopy
    • Saline preparation stool/rectal swab
    • Pus cells
    • RBCs
    • Trophozoites
      • Entamoeba histolytica
      • Giardia lamblia
      • Balantidium coli
    • Cysts
      • Entamoeba histolytica
      • Giardia lamblia
  • 40.
    • Methylene Blue Preparation
    • Pus cells
    • Iodine Preparation
    • Cysts of Entamoeba, Giardia
    • Modified ZN Stain
    • Cryptosporidium, Isospora belli
    • Fluorescent Staining
    • Cryptosporidium parvum
    • Gram’s Staining
    • Food Poisoning cases
  • 41. Special Cultures
    • Campylobacters
    • Skirrow’s or Preston medium
    • Microaerophilic conditions
    • Temp 42 o C
    • Yersinia enterocolitica
    • Yersinia Selective Agar
    • Clostridium difficile
    • Anaerobic Blood Agar
  • 42. Other Investigations
    • Stool Antigen Detection By ELISA
    • Giardia, Entamoeba, Rota virus, Norwalk virus
    • Clostridium difficile Toxin Detection
    • Latex agglutination
    • ELISA, Neutralisation tests
    • Electron Microscopy
    • Enteric Adeno, Norwalk and Astro viruses
    • Procto-sigmoidoscopy
    • Pseudomembranous colitis, Amoebic colitis
  • 43. Treatment
    • Fluid Replacement
    • Oral
    • Intravascular
    • Antimotility Agents
    • Antisecretory Agents
    • Antibiotics
    • Extremes of age
    • Toxic patient
    • Profound deyhydration
    • Probably having bacteremia
    • Blood and mucus in stools
    • Immunocompromised
  • 44. Treatment
    • Antibiotics
    • Conventional Agents
    • Ampicillin
    • Co-trimoxazole
    • Tetracycline
    • Chloramphenicol
    • Metronidazole
    • Other Agents
    • Nalidixic acid
    • Norfloxacin
    • Ciprofloxacin and other FQs
    • Doxycylcline, Minocycline
    • Cephalosporins
    • Newer Macrolides
  • 45. 2. Duration of diarrhea
    • ACUTE (symptoms  14 days)
      • sudden onset, 90% are infectious in etiology
      • Community-acquired:
        • Gram-negative bacterial pathogens
        • Viral pathogens
          • Norovirus
          • Rotovirus
        • Protozoal pathogens
          • Entamoeba histolytica
      • Nosocomial (> 3 days after hospitalization)
        • Clostridium difficile
      • Travelers:
        • ETEC
  • 46.
    • PERSISTENT/CHRONIC (symptoms > 14 days)
      • Most of the causes are non-infectious
      • Parasitic
        • Giardia lamblia, Cryptosporidium parvum, Cyclospora, Isospora belli
      • Immunocompromised host
        • Also consider Microsporidium and CMV
  • 47. 3. Low-versus high-volume diarrhea
    • Low volume (low water): colonic
    • High volume (high water): small bowel
      • OSMOTIC DIARRHEA: high-volume diarrhea in which the measured fecal osmolality is less than 2 [Na + K]
        • Sorbitol-containing liquid medications, tube feedings, lactose intolerance
      • SECRETORY DIARRHEA: high-volume diarrhea in which the measured fecal osmolality equals 2 [Na + K]
        • E. Coli , rotavirus, laxative abuse
  • 48. 4. Small- versus large-bowel diarrhea
    • Small bowel
      • Large volume, watery, less frequent, painless stools
      • Blood and WBCs are rare
      • Proctoscopy is normal
      • Pain is mid-abdominal
    • Large bowel
      • Small volume, often mucoid, more frequent, painful stools
      • Blood and WBCs are common
      • Proctoscopy is abnormal
      • Pain is lower-abdominal (left lower quadrant)
  • 49. Case History
    • A 40-year-old woman presented with diarrhea. She had had loose stools for 2 years, progressing over the past 6 months to fifteen large-volume watery stools daily.
    • What is your differential diagnosis?
    • What diagnostic and management steps would you choose?
  • 50.
    • Differential Diagnosis
      • Celiac disease
      • IBS
      • Lactose intolerance
      • Intestinal TB
      • Intestinal worms
      • Cryptosporidium parvum secondary to AIDS
      • HUS
      • Cancer colon
      • This case is a transition from semi-solid to watery diarrhea which is a classical hallmark of progressive ileal disease . When less than 50-60% ileum is involved, there is fat malabsorption and semisolid stools. But when more than 50% of ileum is involved, it will also lead ultimately to bile salt malabsorption
  • 51.
    • Investigations
      • Stool analysis, C/S, serum electrolytes (Na, K, Ca), electrolytes, CBP
      • Anti-gliadin/endomysial antibody testing to r/o celiac
      • ELISA
      • Barium swallow/enema, colonoscopy
    • Treatment
      • Fluid replacement
        • Oral
      • Antimotility agents