NON-PATHOGENIC
&
OPPORTUNISTIC
AMOEBAE
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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
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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 times
Red blood cells are seen very rarely
Nuleus: spherical;central karyosome
Chromatin granules are closely packed
TRANSMISSION: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
structures
No peripheral chromatin. Reproduction is by simple
binary fission
FLAGELLATE:Non-dividing,non-feeding form
CYST: 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..
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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 acanthopodiatapering 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 tissue
Keratitis: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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