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
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