Entamoeba histolytica-like amoebae occurring in man.

Six Entamoeba histolytica-like amoebae of the Laredo-type are compared with classical E. histolytica strains with regard to morphology, temperature-tolerance, response to hypotonic solutions, antigenic make-up, pathogenicity, sensitivity to drugs, and biochemistry. Sharp discontinuities are shown to exist between the 2 groups in some parameters, sufficient, under certain conditions, to justify creation of a new species designation for the Laredo-type amoebae. Nevertheless, this action is not recommended at the present time because of the small number of "aberrant" strains so far isolated, and because of the limited comparative studies so far carried out.Entamoeba moshkovskii is compared with the Laredo-type E. histolytica. No consistent distinction can be made between the 2 groups except for the sources of the strains-the former is free-living and the latter parasitic. It is therefore suggested that E. moshkovskii may actually be a parasite of the Laredo type, only incidentally encountered in free-living environments because of its wide temperature and tonicity tolerances. Since, here too, only limited studies are so far available, it is suggested that the term "moshkovskii-like E. histolytica" be used until sufficient data are accumulated to assign these amoebae to a more precise location in the taxonomic scheme.