AN IMPROVED COLORIMETRIC PCR-BASED METHOD FOR DETECTION AND DIFFERENTIATION OF ENTAMOEBA-HISTOLYTICA AND ENTAMOEBA DISPAR IN FECES

The epidemiological implications of the recent separation of ''Entamoe ba histolytica'' into two separate species, pathogenic E. histolytica sensu stricto and commensal E. dispar, will not become apparent withou t methods of distinguishing between them which are applicable to large numbers of specimens. We have modified a PCR-based method to produce such a technique which may be completed in 1 day while still identifyi ng 10(-1) E. histolytica and 1 to 10 E. dispar trophozoites per g of f eces when present separately and 10 E. histolytica and 100 E. dispar t rophozoites per g in the presence of 10(6) trophozoites per g of the o ther species. Applied to fecal specimens from 18 patients from which E . histolytica or E. dispar had been grown and identified to the specie s level by hexokinase isoenzyme analysis, the method in every case yie lded the correct result. Positive and negative results are easily dist inguished by eye, and we are now applying this technique to a large-sc ale epidemiological study of amebiasis in the eastern Mediterranean re gion.