Free Living Amoeba: Acanthamoeba spp. & Naegleria fowleri

This set of vocabulary flashcards covers the biology, morphology, clinical manifestations, and diagnosis of free-living pathogenic amoebae, specifically Acanthamoeba spp. and Naegleria fowleri.

Free Living Amoeba (FLA)

Small, free-living organisms widely distributed in soil and water.

Amphizoic

The ability of an organism to live freely in the environment or as an endoparasite within a vertebrate host.

Phagotroph

An organism that feeds on aquatic bacteria, which is the typical role of free-living amoebae.

Granulomatous Amebic Encephalitis (GAE)

A serious, slow-developing (insidious) infection of the central nervous system caused by Acanthamoeba spp., typically affecting immunocompromised individuals.

Acanthamoeba Keratitis (AK)

A severe and painful eye infection caused by Acanthamoeba spp., often associated with contact lens use or eye trauma.

Acanthopodia

Spiky or spine-like pseudopodia characteristic of the Acanthamoeba trophozoite stage.

Acanthamoeba Trophozoite

The active and infective stage of Acanthamoeba, measuring $20-45\,\mu\text{m}$, featuring a single nucleus with a large karyosome and sluggish movement.

Acanthamoeba Cyst

The dormant, resistant stage measuring $10-25\,\mu\text{m}$ with a double-layered cell wall consisting of a wrinkled ectocyst and a smooth, variable-shaped endocyst.

Ring Infiltrate

A clinical 'red flag' sign of Acanthamoeba Keratitis involving corneal stroma necrosis.

Non-Nutrient Agar (NNA) with E. coli

The gold standard laboratory culture technique for diagnosing Acanthamoeba Keratitis, where trophozoite migration tracks can be observed.

Naegleria fowleri

Commonly known as the 'brain-eating amoeba,' it is a thermotolerant organism that causes Primary Amebic Meningoencephalitis (PAM).

Thermotolerant

The ability of an organism, such as Naegleria fowleri, to tolerate and thrive in heat, such as warm fresh water or hot springs.

Lobopodia

Broad, blunt pseudopodia characteristic of the Naegleria fowleri trophozoite.

Promitosis

The method of reproduction for Naegleria fowleri trophozoites where the nuclear membrane remains intact during division.

Flagellated Stage (Naegleria)

A temporary, non-feeding, pear-shaped stage with $2$ flagella that moves quickly; it is not found in brain tissue.

Primary Amebic Meningoencephalitis (PAM)

A rare but nearly always fatal ($>97\%$) brain infection caused by Naegleria fowleri entering through the nasal passages.

Olfactory Nerve

The pathway through which Naegleria fowleri migrates from the nasal cavity to the brain.

PHMB and Chlorhexidine

Chemical agents used in the treatment of Acanthamoeba Keratitis (AK).

Ensistasi (Encystment)

The process where an amoeba transforms into a cyst stage when facing extreme environmental conditions.