Amoeba

AMOEBA

Sarcodina:
1- Entamoba histolytica.
. 2- Entamoba coli
. 3- Entamoeba gingivalis
. 4- Entamoba dispar
5- Endolimax nana.
. 6- Dientamoeba fragilis
. 7-Naegleria fowleri
8 –Acanthamoeba spp.

Entamoba histolytica
Causes amoebiasis , an infection of large intestine in man . The causative agent of amoebic dysentery, Three stages have been described in to the morphology of E.histolytica , There are trophozoite , precyst ,cyst.

Morphology of trophozoite
The size of troph 8-65 mm, the shape is round and have one nucleus . Also have one pseudopodia ,therefore movement is unidirectional.
The cytoplasm are finely granular , karyosome is central, and peripheral chromatin is evenly distributed . Red blood cell in the cytoplasm are considered diagnostic because E. histolytica is only intestinal amoeba to exhibit this characteristic

Cyst:
From 2 -4 nuclei depending on maturity level and Diameter of cyst 10- 15 m m. The karyosome is also central .

Life cycle :
The quadrinucleate cyst is the infective form of parasite and is resistant to chlorination ,gastric acidity and desiccation And can survive in moist environment for several weeks.
Infection with E. histolytica occurs due to fecal- oral spread with fecally contaminated food and water . the excystation of cyst occurs in the small intestine, where the cyst under goes nuclear and cytoplasmic division to form eight trophozoites .
the trophozoites can colonize and / or invade the large bowel, Cyst are never found within invaded tissues, Invasion of the colonic intestinal epithelium by trophozoites lead to the formation of the classically described flask – shaped ulcers.
hepatic abscesses are thought to occur due to migration of the parasite via the portal vein .
All infections with E. histolytica are not a like ,and whether infection result in colonization or invasion may be influenced by the E. hitolytica strain and its interaction with bacterial flora .
In some patients , the trophozoites invade the intestinal mucosa (intestinal disease ) or through the blood stream , extra intestinal sites such as the liver ,brain , and lung ( extra intestinal disease ) with resultant pathogenic manifestation.