FREE LIVING

AMOEBA

DR. HALA ELNAHAS

PBL 4

AZFARFATHULLAH

FIRDAUSREZA

NOREENSAFWABALQISSARAHANEESAINTANHANIE

PATHOGENIC FREE LIVING AMOEBA

OBJECTIVES: Types of amoeba General characters of free living amoeba Definition of amphizoic amoeba Naegleria fowleri and Acanthamoeba -Characters -Habitat -Morphology -Mode of infection -Pathogenesis -Clinical picture -Diagnosis -Treatment -Prevention

Amoeba

Parasitic

Free living

PathogenicE. Histolytica

CommensalEntamoeba coli

Iodamoeba butschili

Naegleria fowleri

Acanthamoeba castellani

Free living amoebae comprise a large group of protozoa living in moist soil, decaying vegetation and in all types of water, especially water containing bacteria.

Several species have been observed as human symbionts without pathological consequence, although some of them may result in severe disease.

Two genera are known to produce diseases in man:1- Naegleria fowleri (an amoeboflagellate). 2- Acanthamoeba castellani.

GENERAL CHARACTERS OF FREE LIVING AMOEBA

Naegleria fowleri

Acanthamoeba castellani

AMPHIZOIC AMOEBA

They have also been called amphizoic amoebae because these amoebae have the ability to exist as free-living organisms in nature and only occasionally invade a host and live as parasites within host tissue.

Character Naegleria fowleri

Acanthamoeba

Forms 3 stages• Trophozoite• Flagellate• Cyst

2 stages• Trophozoite• Cyst

Trophozoite Actively mobile Sluggishly mobile

Cyst Round Polyhedral

Naegleria fowleri

Acanthamoeba

HABITAT Environment: Soil and fresh waterMan: CNS

•Environment: soil ,dust and fresh water•In man: CNS,eyes,skin,lungs

MORPHOLOGY Amoebo-flagellate

1)Trophozoitea.Amoebic :•Trophozoite takes the amoebic form in tissues and CSF

Both stages may exist in the environment and tissues1)Trophozoite• 10-40µ• Pseudopodia are in

the form of multiple small spiky processes surrounding the body

• Nucleus has large central karyosome

Naegleria fowleri Acanthamoeba

•Size 10-15µ,nucleus has large central karyosome and no peripheral chromatin•Multiplication by longitudinal binary fissionb) Flagellate:• Amoeba changes to

flagellated form if get in contact with warm water/CSF

• 2 long equal flagellaec) Cyst• In soil,never in tissues• Rounded,7-10µ,

uninucleated• Wall is smooth,has no

pores

b)Cyst•15-20µ,more or less rounded•Has double wall,outer smooth irregular ectocyst and inner rough polyhedral endocyst provided with many pores (osteoles)•It is mononucleated•It can exist in the tissues

Naegleria fowleri Acanthamoeba

MODE OF INFECTION Through the nasal route

1.Swimming or sniffing in contaminated water2.Inhalation of contaminated air

-Trophozoite in contaminated water enters the nosemigrates through the nasal mucosacribriform plateolfactory nerveolfactory pulpbase of the braindisseminates to the brain tissue

Mode of infection:•Inhalation of aerosol or dust containing cyst or trophozoites•Invasion through broken skin•Sniffing in contaminated water•Corneal trauma, prolonged use of contact lenses

Portal of entry:•Skin,mucosal ulcer,lung inhalation or cornea

PATHOGENESISPAM ( Primary

Amoebic Meningo-

encephalitis)

• Children & young

adult

• Previously healthy

• Headache, temp 38-

40⁰C

1)Granulomatous amoebic encephalitis • Affect

immunocompromised person

• Tissue contain trophozoite , cyst and multinucleated giants cell

2) Amoebic keratitis• Trophozoite & cyst are

present in corneal tissues

3)Chronic granumalatous skin ulcer

Amoeba affecting brain Amoeba affecting skin

• 1ry amoebic meningoencephalitis (PAM)

• Granumolatous amoebic encephalitis

• Amoebic brain abcess

• Granulomatous skin ulcer• Cutaneous amoebiasis

Pathogenesis and Clinical Picture

Amoeboid trophozoite

Nasal mucosa

Cribriform plate

Olfactory nerve

Brain, meninges

Diffuse meningoencephalitis with haemorrhage and necrosis of brain tissue

Fever, headache, nausea, vomiting, stiffness of neck (Kernig’s sign), convulsions.

Disturbance in the sense of smell and taste

Coma and death within 3-6 days from infection

Thus Naegleria causes acute fulminant rapidly fatal disease

20

Acanthamoeba species

Granulomatous Amoebic Encephalitis

Acanthamoeba Keratitis

21

Diffuse meningoencephalitis.

Runs rapidly fatal course (death within 3-6 days)

History of swimming in natural water or swimming pools.

Focal, granulomatous, space-occupying lesion.

Runs sub-acute or chronic course (lasts for weeks, months or years)

Not strongly associated with swimming.

Naegleria meningoencephalitis

Acanthamoeba encephalitis

Children & young adults

Debilitated Chronically ill low immunity

22

DIAGNOSIS • Recent History• Laboratory diagnosis 1. Brain tissue biopsy 2. CSF Examination 3. CSF culture 4. Animal inoculation• Serodiagnosis not

useful

• Brain tissue & CSF : Trophozoite & cyst

• Culture on non nutrient agar

• CSF elevated protein , normal or decrease glucose

• Corneal scrapping• Culture of contact

lens saline • IFA of tissue• Ct multiple brain focal

tissue

TREATMENT • No satisfactory treatment

• Hospitalization • Palliative treatment• Amphotericin B +

Miconazole or Rifampicin

• No effective treatment is available

• Sulfadiazine,penicillin and chloramophenicol

• In keratitis, drug is effective (ketoconazole) + topical application ( miconazole followed keratoplasty

PREVENTION • Public education• Chlorination of

swimming pools and public water supplies

• In high-risk areas, monitoring of recreational waters for N. fowleri amoebae should be considered by local public health authorities and appropriate warnings posted, particularly during the hot summer months.

• Health education

• Avoid swimming in stagnant water

• Use of proper contact lens fluid

THANK YOU !!!