1. Free-Living Amoebae
Dr. Amira Taman

2. Entamoeba histolytica -Acanthamoeba castellani
Amoebae
Parasitic
Pathogenic
Entamoeba histolytica
Commensal
Entamoeba coli
Free-living
-Naegleria fowleri
-Acanthamoeba castellani

3. General characters (free-living)
Opportunistic pathogens in human (under unknown conditions).
Widely distributed in soil and water.
Naegleria fowleri and Acanthamoeba castellani

4. Features
Intestinal amoebae
Free-living amoebae
Habitat
Pathogenicity
Flagellated forms
Intestine
Pathogenic (diseases in colon, liver and other extra-intestinal sites)
Absent
Soil and water
Opportunistic (affect CNS, cornea and skin)
May be present

5. Naegleria fowleri Morphology Amoebo-flagellate Three forms Amoeboid
Free-living in fresh or brackish water (lake, river and ponds) and soil.
Morphology
Amoebo-flagellate
Three forms
Amoeboid
Flagellate
Cyst

6. Amoeboid (Trophozoite )
Rounded / elongated 15-30u.
The infective stage
Single nucleus
Feed and divide by binary fission.
Can be transformed into flagellate and cyst form
Found in CSF and tissue

7. Flagellate form Elongated / pear shaped Anterior nucleus
Two free flagella
Found in water at ̊C
Non feeding & non dividing
Never present in tissue
Can be transformed to amoeboid form

8. Cyst form Rounded with single nucleus 7-15u Thick double cyst wall
Found in soil
Never in tissue

11. Infection
Swimming or diving in warm water(aspiration of water) contaminated with N. Fowleri (trophzoite) esp. in summer.
Trophozoit is neurotropic ( nose- olf mucosa-olf pulb-cribriform plate-subarachinoid space).
1ry amoebic meningoencephalitis (fatal)
- haemorrhagic inflammation
- necrosis of brain tissue
- Amoeba is the only form detected in brain tissue, flagellates and cysts never found in tissue or CSF

12. 1ry amoebic meningoencephalitis
Children and young adult
Previously healthy
History of bathing, swimming, diving or playing in warm stagnant, fresh water
Few days to 2 weeks prior to onset of symptoms
Headache, temp
Stiff neck, mental status changes and seizures

13. Diagnosis History of swimming in pools or natural warm water
Clinical picture
CSF fresh film (amoeboid), purulent but no bacteria. Increase pressure, PMN cells , increase protein, presence of RBCs
Stained : giemsa, trichrome and Wright stains
Culture on non-nutrient agar plate seeded with E. Coli
Leucocytosis in peripheral blood (25,000)
Serodiagnosis not useful, PCR, CT

14. Treatment of PAM No satisfactory treatment. Hospitalization
Palliative treatment
Amphotericin B “drug of choice”.
Act on amoebic plasma membrane .
IV or intrathecal
Miconazole, rifampin and sulfisoxazole.

15. Prevention Public education
Chlorination of swimming pools and public water public supplies

16. Acanthamoeba castellani
In dust, soil, sand, river ponds and tape water.
2 forms: Trophozoite and Cyst (infective stages).
Both stages may exist in the environment and tissues.
In man : affect CNS, eye, skin and lungs.
Opportunistic parasite, causes severe disease in immunocompromised.

17. Trophozoite Variable in shape 10-40 u in diameter
slender spine-like projections of plasma membrane (acantopodia).
Contractile vacuole
Nucleus with large central karyosome

18. cyst Polygonal, spherical; or star- shaped. 15-20u in diameter
Double wall, outer smooth irregular ectocyst and inner rough polyhedral endocyst with many pores (osteoles)

20. Inhalation of aerosol or dust containing cyst or trophozoites.
Portal of entry
Skin, mucosal ulcer, lung inhalation or cornea.
Mode of infection
Inhalation of aerosol or dust containing cyst or trophozoites.
Invasion through broken skin.
Corneal trauma, prolonged use of contact lenses.

22. Diseases Affects immunocompromised
1) Granulomatous amoebic encephalitis:
Affects immunocompromised
Course is sub-acute or chronic (from weeks to years)
Reaches brain through blood supply from lung or skin abrasions.
forms focal granuloma at deeper brain tissues
Headache, seizures, stiff neck, nausea and vomiting
Tissues contain Trophozoite, cysts and multinucleate giant cells.

23. 2) Amoebic keratitis:
Direct contact of cornea with contaminated water or contact lens
Chronic progressive, ulcerative keratitis
Severe unilateral ocular pain
Vision is affected, neutrophils infiltrations
Loss of vision
Trophozoite and cyst are present in corneal tissue
3) chronic granulomatous skin ulcers

24. Laboratory diagnosis Brain tissue and CSF Trophozoite and cyst
Culture on non nutrient agar
CSF elevated protein, normal or decrease glucose.
Corneal scraping (direct saline wet mount)
Culture of contact lens saline or corneal scraping
CT multiple brain focal lesions.
IFA of tissue.

25. Treatment Health education Avoid swimming in stagnant water
No effective therapy is available
Sulfadiazine, penicillin and chloramophenicol.
In keratitis, drug is effective (ketoconazole) with topical application ( miconazole) followed by keratoplasty.
Prevention
Health education
Avoid swimming in stagnant water
Use of proper contact lens fluid

26. Characters
Naegleria
Acanthamoeba
Forms
Trophozoite
Cyst
3 stages
Trophozoite, flagellate and cyst
Actively motile
Round
Two only
Trophozoite and cyst
Sluggishly motile
polyhedral

27. 1ry amoebic meningoencephalitis (PAM)
Amoeba affecting brain
1ry amoebic meningoencephalitis (PAM)
Granulomatous amoebic encephalitis (GAE)
Amoebic brain abscess.
Amoeba affecting skin
- Granulomatous skin ulcer
- Cutaneous amoebiasis