Amoeba

• Protozoa


  Unicellular protists classified under Kingdom Protista
• Protozoa


  • Lack cell wall
  • Contains an outer membrane called periplast
  • Cytoplasm contains ectoplasm (outer region) and endoplasm (inner region with organelles)
  • Distinguishable by their RNA
  • Contain enzymes like hyaluronidase for dissolving debris and facilitating pathogenesis
• Nucleus


  Contains karyosome - mass of chromatin or genetic materials, can be centrally or eccentrically located
• Locomotion structures


  • Cilia - short hair projections
  • Flagella - long hair projections
  • Pseudopods - outer membrane extensions
• Cytostome

  Primitive mouth
• Cytopyge

  Anus of the parasite
• Cyst


  Dormant, survival stage that is non-motile, non-feeding, and non-reproducing. Infective stage.
• Trophozoite


  Feeding/vegetative stage that is motile and reproducing/replicating/dividing
• Excystation


  Cyst to trophozoite transition requires temperature, pH, and moisture
• Encystation


  Trophozoite to cyst transition occurs in the absence of temperature, pH, and moisture
• Entamoeba histolytica


  Causes intestinal and extraintestinal amoebiasis (amoebic dysentery)
• Incubation period for Entamoeba histolytica is highly variable, ranging from 4 days to 4 months
• Infective form of Entamoeba histolytica

  Mature quadrinucleate cyst passed in feces of convalescents and carriers
• Mode of transmission for Entamoeba histolytica

  Man acquires infection by swallowing food and water contaminated with cysts
• Entamoeba histolytica cyst


  • Size 10-20 μm
  • With fine even peripheral chromatin
  • Usually with 1-4 nuclei divided by mitosis
  • Thin nuclear membrane
  • Contains chromatoid bodies or chromotoidal bars (mass of RNA, cigar shaped)
  • Resistant to gastric acidity and desiccation
• Entamoeba histolytica trophozoite


  • Size 10-60 μm
  • With finger-like, sharply pointed pseudopods
  • Progressive, rapid and unidirectional movement
  • With fine even peripheral chromatin
  • Cytoplasm has ground glass appearance
  • Presence of ingested RBCs
  • Appearance of karyosome is bull's eye
  • Reproduces by binary fission
• Clinical manifestations of intestinal amoebiasis include large, foul-smelling, brownish black stools with blood-streaked mucus, presence of clumped RBCs, and Charcot-Leyden crystals
• Clinical manifestations of hepatic amoebiasis include liver abscess containing thick chocolate brown pus, flask shaped lesions in hepatocytes, and jaundice
• Laboratory diagnosis methods for Entamoeba histolytica

  • Wet preparation
  • Permanent staining technique
  • TYI-S-33
  • ELISA
  • Indirect hemagglutination
  • Gel diffusion precipitin
  • Indirect immunofluorescence
• Treatments for Entamoeba histolytica

  • Paramomycin
  • Diloxanide furoate (Furamide)
  • Metronidazole (Flazyl)
• Entamoeba coli


  Non-pathogenic commensal intestinal amoeba
• Entamoeba coli cyst


  • Size 10-30 μm
  • With a prominent glycogen mass in the early stage
  • Chromatoid bodies are splinter-like and irregular
  • Mature cyst has 8-16 nuclei
  • Karyosome is large and eccentrically located
• Entamoeba coli trophozoite


  • Size 20-50 μm
  • With sluggish motility and contains ingested bacteria but no red cells
  • Nucleus is clearly visible with thick nuclear membrane lined with coarse chromatin granules
• Entamoeba hartmanni


  Non-pathogenic commensal intestinal amoeba
• Entamoeba hartmanni cyst


  • Size 5-10 μm
  • Irregularly shaped, resembles Endolimax nana
• Entamoeba hartmanni trophozoite


  • Size 4-12 μm
  • Trophozoites do not ingest red blood cells
  • Motility is less vigorous
• Entamoeba polecki


  Causes diarrhea
• Treatments for Entamoeba polecki

  • Metronidazole (Flagyl)
  • Diloxanide (furamide)
  • Albendazole
• Entamoeba polecki cyst


  • Size 10-20 μm
  • Spherical to oval shape
  • Contains one nucleus
  • Granular cytoplasm
  • Has chromatoid bars (not confirmed)
• Entamoeba polecki trophozoite


  • Size 8-25 μm
  • Normal stool: sluggish and nonprogressive
  • Diarrheal stool: progressive, unidirectional
  • Granular and vacuolated cytoplasm
  • May contain ingested bacteria and other food particles
• Endolimax nana


  Non-pathogenic commensal intestinal amoeba
• Endolimax nana cyst


  • Size 4-12 μm
  • Spherical, ovoid, ellipsoid shape
  • 1-4 nuclei
  • Karyosome is large, blot like and usually central
  • Chromatoid bars are NOT present
• Endolimax nana trophozoite


  • Size 5-12 μm
  • Motility is sluggish, nonprogressive, with blunt pseudopods
  • 1 nucleus
  • Karyosome is large, irregular, and blot like
• Iodamoeba butschlii


  Iodine loving parasite
• Iodamoeba butschlii cyst


  • Size 5-22 μm
  • Ovoid, ellipsoid, triangular, or other shapes
  • 1 nucleus
  • Large karyosome, eccentric achromatic granules on one side
  • Cytoplasm has well defined glycogen mass
• Iodamoeba butschlii trophozoite


  • Size 8-20 μm
  • Motility is sluggish and nonprogressive
• Endolimax nana


  • Small, uninucleate, non-invasive, unidirectional
  • Granular and vacuolated cytoplasm
  • May contain ingested bacteria and other food particles
• Cyst


  • Size: 4-12 µm
  • Shape: Spherical, ovoid, ellipsoid
  • Nuclei: 1-4
  • Karyosome is large, blot like and usually central
  • Chromatoid bars are NOT present
• Trophozoite


  • Size: 5-12 µm
  • Motility: Sluggish, nonprogressive, blunt pseudopods
  • Nuclei: 1
  • Karyosome is large, irregular, and blot like
• Cyst


  • Size: 5-22 µm
  • Shape: Ovoid, ellipsoid, triangular, other shapes
  • Nuclei: 1
  • Large karyosome, eccentric achromatic (cannot take up the stain) granules on one side
  • Cytoplasm is well defined glycogen mass