DNA characterization of simian Entamoeba histolytica-like strains to differentiate them from Entamoeba histolytica.

Two simian Entamoeba histolytica-like strains, EHMfas1 and P19-061405, have been suggested to represent a new species based on genetic characterization. Sequence analyses of the hexokinase, glucose phosphate isomerase, and phosphoglucomutase genes supported the previous findings of isoenzyme analyses demonstrating a new zymodeme pattern. Phylogenetic studies of 18S rDNA, 5.8S rDNA, the chaperonin 60 gene, and the pyridine nucleotide transhydrogenase gene showed original clusters of simian E. histolytica-like strains below or near E. histolytica, respectively. Comparative studies of the chitinase and the serine-rich E. histolytica protein genes and locus 1-2 region revealed that most mutated units were shared among the simian E. histolytica-like strains. The similarities of each of the repeating units within the simian E. histolytica-like strains or E. histolytica and the differences of those between the both might be generated by concerted evolution. Our results indicate that EHMfas1 and P19-061405 should be considered to be the same species, despite that they were isolated from different monkey species and different habitats. Simian E. histolytica-like amebas may be endemic to macaque monkeys, as a counterpart to E. histolytica in humans, and should be differentiated from E. histolytica by the revival name Entamoeba nuttalli, as proposed for P19-061405.