Studies on the pathogenesis of Acanthamoeba-associated meningoencephalitis

100 indoor swimming pools were examined for the presence of free-living amoebae. Limax amoebae of the genus Acanthamoeba could be isolated from 34 samples. Naegleria spp. were not present. After axenic cultivation the pathogenicity in mice was tested. Histological as well as immunohistological procedures were compared in order to identify the amoebae in brain sections and to clarify the route of infection. The results indicate a direct invasion of the central nervous system by acanthamoebae via the nasal mucosa and the olfactory bulb.