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Dr.%20Amira%20Taman
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Free-Living Amoebae Dr. Amira Taman General characters (free-living) ... Serodiagnosis not useful, PCR, CT Treatment of PAM No satisfactory treatment. – PowerPoint PPT presentation
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Title: Dr.%20Amira%20Taman
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Free-Living Amoebae
- Dr. Amira Taman
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General characters(free-living)
- Free-living
- Opportunistic pathogens in human (under unknown
conditions). - Widely distributed in soil and water.
- Naegleria fowleri and Acanthamoeba castellani
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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
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Naegleria fowleri
- Free-living in fresh or brackish water (lake,
river and ponds) and soil. - Morphology
- Amoebo-flagellate
- Three forms
- Amoeboid
- Flagellate
- Cyst
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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
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Flagellate form
- Elongated / pear shaped
- Anterior nucleus
- Two free flagella
- Found in water at 27-37 C
- Non feeding non dividing
- Never present in tissue
- Can be transformed to amoeboid form
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Cyst form
- Rounded with single nucleus
- 7-15u
- Thick double cyst wall
- Found in soil
- Never in tissue
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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
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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 38.2-40
- Stiff neck, mental status changes and seizures
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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
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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.
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Prevention
- Public education
- Chlorination of swimming pools and public water
public supplies
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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.
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- Trophozoite
- Variable in shape 10-40 u in diameter
- slender spine-like projections of plasma
membrane (acantopodia). - Contractile vacuole
- Nucleus with large central karyosome
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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)
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- 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.
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- Diseases
- 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.
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- 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
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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.
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Treatment
- 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
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Characters Naegleria Acanthamoeba
Forms Trophozoite Cyst 3 stages Trophozoite, flagellate and cyst Actively motile Round Two only Trophozoite and cyst Sluggishly motile polyhedral
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- Amoeba affecting brain
- 1ry amoebic meningoencephalitis (PAM)
- Granulomatous amoebic encephalitis (GAE)
- Amoebic brain abscess.
- Amoeba affecting skin
- - Granulomatous skin ulcer
- - Cutaneous amoebiasis
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