Differentiation between Pathogenic and Non-Pathogenic Entamoeba Histolytica
The spectrum of disease in amebiasis is remarkable. It is estimated that there are approximately 500 million infections/year, but most of them are asymptomatic and only about 10% of the cases develop into disease (1, 2). The prevailing hypothesis was that there are two distinct, albeit morphologically identical, species of E. histolytica, a pathogenic one which can cause disease and the second, a non pathogenic variety which is a commensal and will never cause disease (3). Numerous investigators are searching for biochemical and molecular differences between these two types of amoebae which may support this theory. Martinez-Palomo showed differences in agglutinability by the lectin Concanavalin A in E. histolytica isolates obtained from patients with invasive amebiasis and from symptomless cyst passers (4). Sargeaunt and his colleagues (5, 6) have found that the two classes of amoebae can be differentiated by the electrophoretic migration of two isoenzymes, hexokinase and phospho glucomutase. The main questions that were raised, however, were (I) could persons infected with amoebae that have the non pathogenic isoenzyme patterns ever develop disease, (II) could asymptomatic carriers serve as the source of infection that would have clinical manifestations in other subjects, and (III) should asymptomatic carriers infected with amoebae that possess non pathogenic isoenzymes be subjected to drug therapy. Classification of E. histolytica into pathogenic or non pathogenic species by their isoenzyme electrophoretic patterns appears to be of no significant value because, as previously reported for other protozoa, notably Tetrahymena (7) and Paramecium (8), isoenzyme migration is not always a stable marker.
KeywordsAsymptomatic Carrier Entamoeba Histolytica Phospho Glucomutase Isoenzyme Pattern Stable Marker
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