Biology of Naegleria spp.

The genus Naegleria consists of free-living amoebae widely distributed in soil and freshwater habitats throughout the world. These organisms characteristically undergo transformation from amoebae to flagellates. There are six species of Naegleria: N. fowtleri, N. aiustr(aliensis, N. lov,aniensis, N. griberi, N. jadini, and N. tliorntoni. Each species may be distinguished on the basis of cyst morphology (163, 164, 199-201, 203), temperature tolerance (91), immunologic criteria (221, 234, 235), pathogenicity (17-19), and isoenzyme patterns (51, 53, 55, 94, 111, 155, 167-169). N. gruberi, a nonpathogenic species, was the first member of the genus to be described and has been used extensively to define the molecular biology of cellular differentiation (83). Another species, N. ftmWleri, sometimes called N. aerobia (133, 199, 201) or N. invades (27), is the causative agent of primary amoebic meningoencephalitis (PAME), a rapidly fatal dis-