• Considered a non-pathogen• Cyst and trophozoite are larger than E.

histolytica• A stained smear is required to

differentiate E. coli and E. histolytica trophs

• Cysts contain 8 nuclei• Hyper nucleation is possible resulting to

16 or more nuclei• trophozoites possess a single nucleus

with a characteristically large, eccentric karyosome and coarse, irregular peripheral chromatin

Trophozoites possess a single nucleus with a characteristically large, eccentric karyosome and coarse, irregular peripheral chromatin

 The only species in the genus encountered in humans with more than four nuclei in the cyst stage

CYST TROPHOZOITE

CYST IN TRICHROME TROPHOZOITE IN TRICHROME

Non pathogenicKnown to be the first amoeba in

humans to be describedFound in the mouth between the

gingival pocketsFound in 95% of people with gum

disease and 50% with healthy gums

Cyst stage is not present therefore transmission is through kissing or sharing utensils

Troph are between 10-20 micrometer Pseudopodia presentTroph may be coughed up; should be

differentiated from E. histolytica which can be found in sputum from pulmonary abscess

Morphologically identical with E. histolytica

Different DNA and ribosomal RNA Differentiated through PCR or genome

sequencing Cysts have 4 nuclei that

characteristically have centrally located karyosomes and fine, uniformly distributed peripheral chromatin

Usually measure 12 to 15 µm

Important in studies concerning E. histolytica pathogenicity

Killing of host cells yet it is non-pathogenic, the molecular reason for this is still in question

Three nuclei are visible in the focal plane (black arrows), and the cyst contains a chromatoid body with typically blunted ends (red arrow)

• Trophozoites have a single nucleus• Centrally placed karyosome and uniformly

distributed peripheral chromatin• Erythrophagocytosis (ingestion of red

blood cells by the parasite) is the only morphologic characteristic that can be used to differentiate E. histolytica from the nonpathogenic E. dispar.  However, erythrophagocytosis is not typically observed on stained smears of E. histolytica

Troph of E. histolytica/E. dispar

Troph of E. histolytica with

erythrophagocytosis