preliminary comparative study of entamoeba histolytica and entamoeba dispar by pcr technique in iran

it has been suggested that two distinct species exist within what was originally known as entamoeba histolytica and e. dispar. these are entamoeba dispar for the nonpathogenic and e. histolytica for the pathogenic fonn. differentiation of these two organisms is of great clinical importance since they are morphologically indistinguishable and both fonns can infect the human intestinal cavity. a study was carried out to differentiate e. histolytica from e. dispar by polymerase chain reaction (pcr) using two sets of primers (p11plus p12 and p13 plus p14) specific for either species of ameba. the extracted dna was used for the identification of the species in the stool and culture media by pcr. a total of 16 samples, cysts and trophozoites, were analyzed. in all, 15 samples reacted with e. dispar primers, resulting in the expected 10 i-bp pcr products however, none of these reacted with e. histolytica primers. only one sample reacted with e. histolytica primers. because of high sensitivity of the pcr method and the high risk of laboratory contamination during processing and extracting dna and its polymerization, and because of many existing cultures of e. histolytica in the same laboratory, the chance of contamination can not be ruled out in the single case of e. histolytica. this preliminary study could be an introduction for a pcr -based epidemiological study to detennine the importance of e. histolytica in iran.