Entamoeba histolytica

N-acetylglucosamine is the host receptor for Entamoeba histolytica.

Glycophorin A is the host receptor for Plasmodium falciparum, Heparan sulfate for Herpes simplex virus and Asialo-GM1 for Pseudomonas aeruginosa.

Ref: Harrisons principles of internal medicine, 18th edition, Page: 1014.

• According to the new classification scheme, the eukaryotes have been classified into six clusters or “Supergroups”, namely : Amoebozoa, Opisthokonta, Rhizaria, Archaeplastida, Chromalveolata and Excavata.
• The amoebae that parasitize the intestinal tracts of humans belong to four genera: Entamoeba, Endolimax, Iodamoeba and Blastocystis. They all belong to phylum Amoebozoa, subphylum Conosa, which contains organisms that move by means of cytoplasmic protrusion called PSEUDOPODIUM.

Ans. is `d’ i.e., Nuclear structure retains characteristics of trophozites

“A mature cyst is quadri-nucleate spherical body. Its cytoplasm is clear and hyaline, and the nuclear structure retains the characteristics of the trophozoite” – Chatterjee

Ans. is ‘a’ i.e., Cyst are 8 nucleated

.     Cyst of E. histolytical is quadrinucleate (4 nuclei)

.    Chromatid bodies do not stain with iodine but are seen as refractile oblong bars with rounded ends in preprations with normal saline and as black when stained with iron-haematoxylin.

.   Trophozoites colonize cecum and ascending colon, sigmoid colon, rectum and appendix in order of frequency.

Ans. is ‘b’ i.e., Nuclear membrane with chromatin; ‘c’ i.e., Shows erythrophagocytosis

.  The trophozoites of E. histolytica engulf red blood cells, bacteria, yeast and other debris. The presence of red blood cells in the cytoplasm (erythrophagocytosis) is diagnostic of E. histolytical as it is the only intestinal amoeba to exhibit this characteristic.

.   Nuclear membrane is lined with a single layer of uniformly distributed fine chromatin granules.

.   Karyosome is central in position (not eccentric).

Ans. is ‘d’ i.e., Refractile nucleus

.                    The early cyst contains a single nucleus and two other structures – a mass of glycogen and one to four chromatid bodies.

Ans. is ‘b’ i.e., Shows erythrocyte in cytosol

The motile form of the parasite, the trophozoite, usually lives as a harmless commensal in the lumen of the large intestine where it multiplies and differentiates into a cyst, the resistance form, responsible for transmission of the infection.

Occasionally, trophozoites would invade the intestinal mucosa and produce dysentery or amoeba and spread to other organs.

E. histolytica has a larger capacity to induce phosphatidylserine exposure in the erythrocytes surface, liposomes containing phosphatidylserine or synthetic negatively charged phospholipids, dicetyl phosphate, stimulate E. histolytica actin polymerization, a necessary event for efficient Erythrophagocytosis. 

Ans. is ‘a’ i.e., Isoenzyme pattern

Zymodene

• There are distinct invasive and noninvasive strains of E. histolytica. These strains vary according to their isoenzyme patterns (zymodemes).
• E. histolytica strains have 22 zymodemes of these 10 zymodemes are invasive and 12 are noninvasive. 
• Zymodemes of E. histolytica are identified according to the electrophoretic mobility of 4 enzymes.

1. L-malate : NADP+ Oxidoreductase
2. Phosphoglucomutase (PGM)——– most important
3. Glucose-phosphate isomerase
4. Hexokinase

• Electrophoresis of PGM can show one or more of the 4 bands : a, 13, y and 5. Strains of E. histolytica showing, an absence of a-band together with the presence of 13 band are virulent i.e., invasive.

Ans. is ‘b’ i.e., Philip’s medium 

Cultures media used for cultivation of E.histolytica are :-

1. Boeck and Drbohlav’s medium       

2. Philip’s medium                             

3. Shaffer and Frye’s medium   

4. Jones medium

5. Balamuth’s medium   

6. Diamond’s medium