Naegleria

Excerpt

Naegleria fowleri, a member of the genus Percolozoa,, is also known as the "brain-eating amoeba." It is a eukaryotic, free-living, amoeba named after Malcolm Fowler who described the initial cases of primary amebic encephalitis (PAM) caused by N. fowleri in Australia.

N. fowleri is found in freshwater that is usually contaminated with soil. N. fowleri is thermophilic and grows well at temperatures as high as 45 C. It has 3 stages in its life cycle: cyst, trophozoites, and flagellates. The trophozoite stage is the reproductive stage and can cause invasive human disease. When environmental factors are not amenable to growth, such as in environments with low food sources, the trophozoite can temporarily change to a flagellate form. The flagellate forms can revert to a trophozoite stage when conditions are conducive to growth. When trophozoites are exposed to environmental stresses, they encyst to form a cyst approximately 9 micrometers in diameter. Cysts can withstand extremes of temperatures ranging from above freezing to 65 C but appear sensitive to freezing. The trophozoite forms of N. fowleri feeds on bacteria and fungi in warm waters and can encyst and settle in sediments on the bottom when the water cools during winter.