Amoeba

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trophozoite form

Back 1

Actively motile form, feeding form

Typically have one nucleus in the intestinal amoeba category

destroyed in concentration methods

more likely to be found in liquid stool

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cyst form

Back 2

Immotile form protected by a cyst wall

Readily transmitted to new host

multi-nucleate (if mature)

found more commonly in formed stool

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Entamoeba histolytica - location and transmission

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Found worldwide

Intestinal pathogenic amoeba

transmitted in cyst form in contaminated food, water, or person to person (oral-fecal)

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E. histolytica symptoms

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• Major symptoms include diarrhea, flatulence, and cramping.
• Can progress to an amoebic dysentery (blood and pus appear in stool)
• May become invasive and spread throughout the body and cause abscess formation (especially the liver).
• Causes tissue damage (lyses host cells)

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Non pathogenic amoeba

Back 5

• Entamoeba dispar
• Entamoeba coli
• Entamoba histolytica
• Endolimax nana
• Iodamoeba butschlii

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Naegleria fowleri - location and transmission

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• Free living pathogenic amoeba
• found worldwide in warm freshwater bodies
• acquired during swimming when troph form reaches the brain through the nasal cavity by penetrating the cribriform plate of the ethmoid bone

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7

Naegleria fowleri - pathogenesis

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Primary amoebic meningoencephalitis

Course is rapid and brief

Death in 1 day to 2 weeks

Eats nerve cells

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Naegleria fowleri - detection

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• Examination of spinal fluid, difficult to detect.
• Culture on non-nutrient agar plate.
• Typically found on autopsy

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Naegleria fowleri - forms

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Trophozoite - infective

cyst - not found in human tissue

Flagellate - in water

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Acanthamoeba sp - location and transmission

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A free living amoeba found in soil and freshwater

Enters the lungs or skin and spreads to the spinal fluid

OR

Following contact with contaminated water or contact lens solution (keratitis).

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Acanthamoeba sp - pathogenesis

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• causes Granulomatous amoebic meningoencephalitis - mostly in immunocompromised patients

• more commonly: keratitis - can cause blindness

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Acanthamoeba sp - diagnosis

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• Examination of spinal fluid, corneal scraping –
• Culture on non-nutrient agar plate.
• There is a trophozoite and cyst stage in human tissue.

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E. histolytica/E. dispar troph

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• Trophozoite: Size: 12 – 60 um (typically 20 um). Cytoplasm: fine granular, little to no vacuoles, may have RBC in cytoplasm.
• Nucleus: fine central karyosome, fine-beaded peripheral chromatin
• may see ingested RBC - distinguishes it from E. dispar

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E. histolytica/ E. dispar cyst

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• Size: 10 – 20 um.
• Inclusions: chromatoidal body is rod-shaped with rounded ends (if present).
• Nucleus: 1-4 nuclei, fine central karyosome, fine-beaded peripheral chromatin.

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E. coli troph

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• Size: 15 - 50 um (typically 20-25um).
• Cytoplasm: coarsely granular, vacuolated, “dirty”.
• Nucleus: large eccentric karyosome, irregular coarse peripheral chromatin

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E. coli cyst

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• Size: 10 - 35 um.
• Inclusions: chromatoidal body is rod shaped with splintered ends (if present).
• Nucleus: 1- 8 nuclei, large eccentric karyosome, irregular coarse peripheral chromatin.

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E. hartmanii troph

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• Trophozoite: Size: 5-12 um (typically 20 um).
• Cytoplasm: fine granular, little to no vacuoles, may have RBC in cytoplasm.
• Nucleus: fine central karyosome, fine-beaded peripheral chromatin

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E. hartmanii cyst

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• Size: 5 - 10 um.
• Inclusions: chromatoidal body is rod-shaped with rounded ends (if present).
• Nucleus: 1-4 nuclei, fine central karyosome, fine-beaded peripheral chromatin.

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Endolimax nana troph

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• Size: 6 – 15 um (typically 8 -10 um).
• Cytoplasm: granular and vacuolated.
• Nucleus: karyosome large and irregular, no peripheral chromatin.

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Endolimax nana cyst

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• Size: 5 - 10 um (typically 6 – 8 um), spherical to oval shape.
• Inclusions: none
• Nucleus: 1 – 4 nuclei, large, irregular karyosome, no peripheral chromatin.

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Iodamoeba butschlii - troph

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• Very similar to E. nana troph Size: 8 – 20 um (typically 12 – 15 um).
• Cytoplasm: coarsely granular, vacuolated, “dirty” (ingests bacteria, etc.).
• Nucleus: large, central, no peripheral chromatin.

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Iodamoeba butschlii - cyst

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• Size: 5 – 20 um (typically 10 – 12 um), spherical to oval.
• Inclusion: mass of glycogen (brownish with iodine).
• Nucleus: 1 nucleus, large, eccentric karyosome