NON-PATHOGENIC&

OPPORTUNISTICAMOEBAE

NON-PATHOGENIC AMOEBAE

• Entamoeba dispar• Entamoeba hartmanni• Entamoeba coli• Entamoeba gingivalis• Endolimax nana• Iodamoeba beutschlii

ENTAMOEBA DISPAR• Non-invasive,nonpathogenic• Earlier it was considered as a

nonpathogenic strain of E.histolytica• E.histolytica &E.dispar are

morphologically identical• Cysts of E.histolytica & E.dispar cannot

be differentiated microscopically

ENTAMOEBA HARTMANNI• Earlier considered as small race of E.histolytica• Morphologically similar to E.histolytica• But trophozoites &cysts are smaller and have a

diameter of 4-12µm &5-10µm respectively• Trophozoites never contain ingested red blood

cells• LIFE CYCLE-Similar to E.histolytica• Δ is by measurement of size of the trophozoites

and cysts & absence of red blood cells in trophozoites

ENTAMOEBA COLI• World wide parasite• Nonpathogenic• Habitat-Lumen of large intestine of man• It exists in 3 stages-Trophozoite,Precyst

and Cyst• Life cycle-Similar to E.histolytica

TROPHOZOITES

• Sluggish movement• Cytoplasm is not differentiated into ectoplasm

and endoplasm• They never contain red blood cells • But bacteria and cellular debris is present• Karyosome is eccentric• Nuclear membrane is thick and is lined by

coarse chromatin granules

• CYST• Spherical,15-20µm• Nuclei-1to8• Chromidial bars are filamentous

• PRECYST• Resembles in shape with that of E.histolytica

ENTAMOEBA GINGIVALIS• First parasitic amoebae to be recognised• Commensal in the gingival tissue around the

teeth• Described by Gros in 1849 in the soft tartar

between the teeth• Also found in the diseased tonsils and in the

vaginal & cervical smears from women using intrauterine devices

ENTAMOEBA GINGIVALIS

• Only the trophozoite stage has been found• Encystation probably does not occur• TROPHOZOITE:10-25µm in diameter;• Actively motile by multiple pseudopodia• Cytoplasm:Differentiated into clear ectoplasm

and granular endoplasm• Food vacuoles consists of digested leukocytes

and epithelial cells

Cont…..

Bacteria are seen at timesRed blood cells are seen very rarelyNuleus: spherical;central karyosome Chromatin granules are closely packedTRANSMISSION:By close contact like kissing and

from contaminated drinking utensils

ENDOLIMAX NANA• World wide,nonpathogenic,small amoeba• Habitat:Lumen of large intestine of

humans,primates and pigs• It has 3 stages:Trophozoite,precyst and cyst• TROPHOZOITES are small in size and

cytoplasm is demarcated into ectoplasm and endoplasm

• Motility: Sluggish• Cytoplasmic inclusions:Bacteria, small

vegetable cells and crystals• No red blood cells• NUCLEUS: Large irregular karyosome ,

arranged eccentrically with Achromatic strands

• Chromidial bars and glycogen vacuole are absent

IODAMOEBA BUETSCHLII• Nonpathogenic luminal parasite of large

intestine• TROPHOZOITES:Active in freshly evacuated

unformed stools & sluggish in older stools• Ectoplasm is not well differentiated from

endoplasm• NULEUS relatively large;karyosome surrounded

by refractile globules• Cytoplasmic inclusions:Bacteria and yeast cells• CYST:Uninucleate,Chromidial bars absent.

NAEGLERIA FOWLERI

• MORPHOLOGY• 2 stages:Motile trophozoites and non-motile cysts• TROPHOZOITE:2 forms→Amoeboid & Flagellate AMOEBOID: Amoebostomes- Distinctive phagocytic

structuresNo peripheral chromatin. Reproduction is by simple

binary fissionFLAGELLATE:Non-dividing,non-feeding formCYST: Uninucleate;spherical; mucoid-plugged pores or ostioles in cyst wall

PATHOGENICITY

• Amoeboid form is the invasive stage• INFECTION:Nasal contamination during

swimming or inhalation of dust containing infective forms

• Flagellate and cyst forms could also enter the nose

• Flagellate forms revert to amoeboid forms and the amoeboid forms escape from the cysts in the nose

Life cycle

Amoeboid forms invade nasal mucosa

Cribriform plate

Olfactory nerve

Olfactory bulbs

Posterior regions of the brain., leading to Primary amoebic meningoencephalitis

ACANTHAMOEBA Sp..• Acanthamoeba culbertosoni• A.castellani• A.hatchetti• A.polyphaga• A.rhysodes

MORPHOLOGY

• Acanthamoeba exists as active trophozoites and resistant cysts

• No flagellate form• TROPHOZOITES:24-56µm;larger than that of

Naegleria;• Irregular in appearance due to acanthopodia-

tapering like pseudopodia;Motility-slow• CYST:Double walled and so are quite resistant• Double wall-Outer wrinkled ectocyst and inner

endocyst

PATHOGENICITY• INFECTION:By inhalation of trophozoites and • by direct invasion through broken or ulcerated skin or eye• Trophozoites reach lower respiratory tract→ CNS

through blood stream• It causes Granulomatous amoebic encephalitis(GAE)

in immunosupressed patients• In healthy persons: Acanthamoeba keratitis and

infection occurs by direct contact of cornea with amoebae

• It releases proteases→cytolysis of corneal epithelium

Keratitis

• Diagnosis: GAE:-Demonstration of Trophozoites in CSF or

trophozoites and cysts in brain tissueKeratitis:Trophozoites and cysts in corneal

scrapings(wet mount preparation)TREATMENT: GAE:Total excision of the mass and

treatment with ketoconazole, penicillin and chloramphenicol

Keratitis:Dibromopropamidine+ Propamidine isethionate ointment or drops

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