Free-Living Amoebae Dr. Amira Taman

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

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

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

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

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

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

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

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

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

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

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.

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

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.

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

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)

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.

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.

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

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.

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

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

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