Entamoeba fam

Protozoan Review (Entamoeba histolytica - Iodamoeba butschlii)

1. Entamoeba histolytica

Morphology:

Cyst (Infective Stage)

• Size: 10-20 µm (spherical)

• Nucleus: 1-4 nuclei

• Peripheral Chromatin (PC): Fine, uniform, beaded appearance

• Karyosome (K): Small, central

• Cytoplasm: Finely granular, ground-glass appearance

• Inclusions (I): RBCs

• Chromatoid Body (CB): Elongated bars with blunt, rounded ends (cigar-shaped, sausage-shaped, rod-like)

• Motility: Progressive, directional

Trophozoite (Vegetative Stage)

• Size: 12-60 µm (irregular shape)

• Nucleus: 1 nucleus

• PC: Fine and evenly distributed

• Karyosome: Small, central

• Cytoplasm: Finely granular

• Inclusions: RBCs

• Motility: Progressive, fingerlike pseudopodia

Pathogenesis:

• Only known pathogenic amoeba

• Can cause: Intestinal and Extraintestinal Amoebiasis

• Asymptomatic cases: 90%

• Intestinal Amoebiasis Symptoms:

• Mucosal invasion leads to flask-shaped ulcers

• Dysentery: Large, foul-smelling stool, brownish-black with blood-streaked mucus

• Charcot-Leyden crystals may be present

• Extraintestinal Amoebiasis:

• Hepatic Amoebiasis (Liver Abscess) → Thick “anchovy sauce pus”

• Pulmonary Amoebiasis: Chocolate brown sputum

Life Cycle:

• Definitive Host: Humans

• Reservoir Host: Humans

• Diagnostic Stage: Cysts, trophozoites

• Infective Form: Mature quadrinucleate cyst

• MOT: Ingestion of food/water contaminated with cysts

Laboratory Diagnosis:

• Stool Examination:

• Direct Fecal Smear (DFS): Fresh stool examined within 30 minutes

• Gold Standard: Concentration technique

• Culture Media:

• Boeck/Drbohlav’s diphasic medium

• Balamuth’s medium

• Robinson & Inoki medium

• Serodiagnosis:

• ELISA, Latex agglutination, Indirect hemagglutination

Treatment:

• Metronidazole (DOC) for invasive amoebiasis

• Diloxanide furoate for asymptomatic carriers

2. Entamoeba dispar

• Morphologically identical to E. histolytica but non-invasive

• More common in sexually active homosexual men

• Affects animals (kittens, gerbils, guinea pigs)

Morphology:

Cyst

• Size: 10-20 µm (spherical)

• Nucleus: 1-4 nuclei

• PC: Fine, uniform, beaded appearance

• Karyosome: Small, central

• Cytoplasm: Granular

• CB: Elongated bars with blunt rounded ends

Trophozoite

• Size: 12-60 µm

• Motility: Progressive

3. Entamoeba hartmanni (“Small race of E. histolytica”)

• Nonpathogenic

• Smaller than E. histolytica

Morphology:

Cyst

• Size: 4-10 µm (spherical)

• Nucleus: 1-4 nuclei

• PC: Fine, uniform, beaded

• Karyosome: Small, eccentric

• CB: Elongated bars with blunt rounded ends

Trophozoite

• Size: 3-12 µm

• Motility: Non-progressive

4. Entamoeba coli (Nonpathogenic commensal amoeba)

Morphology:

Cyst

• Size: 13-30 µm

• Nucleus: 1-8 nuclei

• PC: Coarse, irregular

• Karyosome: Large, eccentric

• CB: Splinter-like (broomstick, jagged ends)

Trophozoite

• Size: 15-50 µm

• Motility: Non-progressive (sluggish), blunt, granular pseudopod

• Cytoplasm: Coarsely granular, vacuolated

5. Entamoeba gingivalis (No cyst stage)

• Resides on teeth surfaces

• May contribute to periodontitis

• Can be found in lungs, cervix, lymph nodes, uterus

Morphology:

Trophozoite

• Size: 10-20 µm

• PC: Finely granular

• Karyosome: Small, central

• Motility: Moderately active, varied pseudopodia

6. Endolimax nana

• Smallest intestinal amoeba

Morphology:

Cyst

• Size: 6-12 µm

• Nucleus: 1-4 nuclei (“Cross-eyed cyst”)

• Karyosome: Large, blot-like, central

Trophozoite

• Size: 8-10 µm

• Motility: Non-progressive

7. Iodamoeba butschlii

Morphology:

Cyst

• Size: 10-12 µm (oval, triangular)

• Nucleus: 1 nucleus

• PC: None

• Karyosome: Large, eccentric with refractile achromatic granules

• Cytoplasm: Large glycogen mass (stains dark brown in iodine prep)

Trophozoite

• Size: 12-15 µm

• Motility: Non-progressive