Geographic origin and spread of pathogenic Naegleria fowleri deduced from restriction enzyme patterns of repeated DNA.

The restriction enzyme patterns of repeated DNA from 20 Naegleria fowleri and 13 N. gruberi strains were compared. On this basis strains of N. fowleri could be easily separated from N. gruberi. Although the restriction enzyme profiles of N. fowleri strains are quite homogenous, strains originating from Europe and from Australia had slightly different patterns. Both European and Australian profiles were found in the USA. In Australia a genetic variant was detected that is the same as the N. fowleri type present in New Zealand. Profiles of strains from India were identical with those from Europe. These results give additional information on the probable origin and dispersal of N. fowleri in the world. Strains of N. gruberi exhibit much more heterogenous banding patterns. Four European N. gruberi strains were, however, nearly identical while two strains from New Zealand had only a single band difference with one restriction enzyme. One Australian strain of N. gruberi was identical to an American strain that has been in culture for almost 30 years. The presence of a virus-like particle in a sister strain of this American isolate did not affect its banding patterns. Other strains of N. gruberi from the USA had diverse restriction enzyme patterns. Adelphamoeba galeacystis has restriction enzyme profiles distinct from those of the Naegleria strains investigated. Isoenzyme analysis in agarose isoelectric focusing confirmed the existence of intraspecific differences in N. fowleri.