NONPATHOGENIC OPPORTUNISTIC AMOEBAE NONPATHOGENIC AMOEBAE Entamoeba dispar Entamoeba

NON-PATHOGENIC & OPPORTUNISTIC AMOEBAE

• • • 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-1 to 8 • 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. . • • • 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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