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[Acanthamoeba spp.] [Balamuthia mandrillaris] [Naegleria fowleri] [Sappinia spp.]

There are two forms of trophozoites in Naegleria fowleri: ameboid and ameboflagellate, only the former of which is found in humans.  The ameboid trophozoites measure 10-35 µm but when rounded are usually 10-15 µm in diameter.  In culture, trophozoites may get over 40 µm.  The cytoplasm is granular and contains many vacuoles.  The single nucleus is large and has a large, dense karyosome and lacks peripheral chromatin.

A	B

A, B: Trophozoites of N. fowleri in culture.

C

C: Ameboflagellate trophozoite of N. fowleri.