Changes in isoenzyme patterns of a cloned culture of nonpathogenic Entamoeba histolytica during axenization

Abstract

The axenization of an Entamoeba histolytica isolate with a nonpathogenic isoenzyme electrophoretic pattern (zymodeme) was recently achieved for the first time (15). Forty days after the cells were transferred to the medium used for axenic cultivation, the amebae developed virulence properties, and the zymodeme converted to a pathogenic pattern. To exclude the possibility that the original isolate consisted of two zymodeme populations and that conditions of growth selected for a particular population, the experiment was repeated with a cloned culture of a nonpathogenic (zymodeme Ill) strain, E. histolytica SAW 1734R clAR, isolated by and obtained from P. G. Sargeaunt. Axenization was accomplished, as before, by transferring trophozoites to TYI-S-33 medium containing a mixture of antibiotics to suppress the growth of the associated bacterial flora and a nutritional supplement consisting of y-irradiated bacteria. A change in the hexokinase and phosphoglucomutase isoenzyme pattern was observed 21 days after the amebae had been transferred to the axenic medium but before complete axenization of the amebae had occurred. The change in zymodeme was accompanied by an increase in virulence, as evidenced by the ability of fewer amebae to induce hepatic abscesses in hamsters. A reverse conversion to a nonpathogenic zymodeme was also accomplished by reassociating and subculturing the newly converted pathogenic trophozoites of strain SAW 1734R clAR with the bacterial flora that accompanied this ameba in the original xenic culture. The electromobilities of the hexokinase isoenzymes changed back to their original pattern 7 days after the amebae were returned to xenic growth conditions. Our in vitro results demonstrate that culture conditions and bacterial flora can cause changes in the zymodeme and virulence of a cloned ameba isolate and raise the concern that this could happen also in vivo. Thus, the finding of a particular zymodeme in a culture of E. histolytica isolated from a carrier should not be used to predict a clinical condition or serve as a basis for the recommendation of therapy.

Identification of a pathogenic isolate-specific 30,000-Mr antigen of Entamoeba histolytica by using a monoclonal antibody

“…Recent studies with DNA probes have indicated that pathogenicity is dependent on genes that are specific to the pathogenic isolates (3,21). On the other hand, it has been observed that isozyme conversion from nonpathogenic to pathogenic, or the reverse, can occur within a cloned culture of a strain of E. histolytica during the process of axenization under appropriate growth conditions (8)(9)(10). Therefore, we cannot exclude the possibility that the gene which codes for the 30,000Mr component may also exist in nonpathogenic isolates.…”

“…Formalinfixed trophozoites were treated with 4G6 (1:20-diluted ascitic fluids) followed by fluorescein isothiocyanate-labeled goat anti-mouse IgG. Note fluorescence on nucleus (arrows) and cytoplasm (arrowhead) of the trophozoites.Bar,10 ,um.…”

Variations in cytotoxicity and isoenzyme patterns of uncloned and cloned cultures of axenic Entamoeba histolytica

“…The recent investigations challenged such a hypothesis since amoebic isolates have been shown to change isoenzyme pattern upon association with bacterial spp. [12][13][14][15]. Such a change could be the result of either the incorporation of a genome of bacteria into genome of amoebae, the selection of a population of amoebae expressing a different isoenzyme pattern, or due to post-translational modifications in amoebae.…”

“…Employing four isoenzymes, namely glucose phosphate isomerase (GPI), maleate NADP oxidoreductase (ME), hexokinase (HK) and phosphoglucomutase (PGM), the isolates of E. histolytica have been shown to have different isoenzyme patterns as compared to isolates from non-invasive amoebic patients [5][6][7][8][9][10][11]. Recently, in vitro transition of a non-pathogenic isoenzyme pattern to pathogenic isoenzyme pattern by co-cultivation of an amoebic culture with bacteria has been observed [12][13][14][15]. Isoenzyme patterns of a population of microbes is considered to be a genetic trait [16].…”

Identification of Significant Variation in the Composition of Lipophosphoglycan‐like Molecules of E. histolytica and E. dispar1

“…Strain virulence refers to the reported capability of producing hepatic lesions in hamsters [4] or the rapid destruction of tissue cultured cell monolayers [ 2 ] . The E. dispar strains SAW 1734R clAR [17] and SAW 760RR clA (documented by Clark and Diamond; [6]) were grown mono-xenically together with C. fasciculata in the absence of bacteria.…”