Parasite biology

Vesicular nucleus with a relatively large, irregularly shaped karyosome anchored to the nucleus by achromatic fibrils

Parasite biology

With large, chromatin-rich karyosome which is surrounded by a layer of achromatic globules and is anchored to nuclear membrane by achromatic fibrils

Life cycle

Stages

Life cycle

Has no cyst stage and does not inhabit the intestine

Life cycle

- Occurs in the alkaline environment of the lower small intestines, releasing metacystic trophozoites that colonize the mucosa of the large intestine

- Non-invasive, does not cause disease

Life cycle

Occurs in the lower colon where the colonic contents

are more dehydrated

Commensal amoeba

• Morphologically similar to E. histolytica, but differ in their DNA and rRNA

• May cause colitis and liver abscess if present in uncontrolled numbers or if host is immunocompromised

• Transmitted via Male-Having-Sex-With-Males (MSM)

• Commonly found in captive primates

• Live and multiply in intestinal crypts of the large intestine mucosa, and feed on starches and mucus secretions

Commensal amoeba

• First detected in sewage

• Morphologically indistinguishable from E. histolytica and E. dispar, but differ from them biochemically and genetically

• Physiologically unique: osmotolerant

• All human isolates belong to one group “ribodeme 2”

Commensal amoeba

• Known as “small-race E. histolytica”

• Relatively similar to E. histolytica but much smaller and more sluggish

• No RBC inclusions

Commensal amoeba

• Cosmopolitan in distribution and considerably more common than other human amebae

• Largest intestinal ameba

• Harmless inhabitant of the colon

• Can survive putrefaction (decomposition/decaying)

• Feed on bacteria, other protozoa, and blood cells (NOT RBCs)

• Used to determine whether water sources are contaminated with fecal wastes

Commensal amoeba

• A parasite found in the intestines of pigs and monkeys

• Zoonotic parasite that can infect humans though cases of infection are rare

• Motility of trophozoites is sluggish

• Morphology:

- Has a small, centrally-located karyosome

- Differentiating characteristic from E. histolytica: uninucleated cysts and angular/pointed chromatoidal bars

Commensal amoeba

• The only amoeba not found in the intestines

• Living on the surface of the gums and teeth, in gum pockets, or in tonsillar crypts

• Exhibit similar morphology with E. histolytica

• No cyst stage

• Acquired through direct transmission (e.g. kissing, droplet spray, utensil sharing)

• NON-PATHOGENIC

Commensal amoeba

• Smallest amoeba

• Occurs with the same frequency as Entamoeba coli (Belizario, 2013)

• Morphology:

- Trophozoites

-- Approx. 5-12 μm and sluggish

-- Have blunt hyaline pseudopodia

--- Nucleus has a large, irregular, blot-like karyosome

- Cyst

-- About the same size as trophozoites and are quadrinucleated when mature

-- “Cross-eyes cyst” with 4 eccentric nuclei

Commensal amoeba

• "Iodine-cyst" because of its affinity to iodine

• Large glycogen vacuole/body which stains deeply with iodine

• Cyst

- Uninucleated resembling a “basket of flowers” shape

- Large glycogen body that stains dark brown with iodine

Commensal amoeba diagnosis

Usually done through _______

Commensal amoeba diagnosis

__________ are recovered from formed stools

Commensal amoeba diagnosis

_______ are recovered from watery or semi-formed stools

Commensal amoeba diagnosis

Stools must be examined within ___________

after passage since trophozoites will most likely die

beyond these times

Commensal amoeba

Used to differentiate between the species

Commensal amoeba treatment