Morphology

Acanthamoeba exists in two forms. The trophozoite (25-40^m) is a proliferative stage, characterized by spine-like pseudopodia (acanthopodia) and slow locomotion. The cell contains a single nucleus with a large, central karyosome, fine granulated cytoplasm with multiple digestive vacuoles, and a prominent pulsating vacuole. The cyst (12-30 •m) a dormant stage, is spherical or star-shaped and has double walls with pores (ostioles) (Martinez 1985) (Figure 8.1). Cysts are highly viable and resistant to a variety of environmental conditions, including ambivalent temperatures, desiccation, amoebicidal drugs, and disinfectants. In a recent report (Mazur et al. 1995), cysts have been demonstrated to retain their viability and virulence even after 24 years of storage.

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