Genetic Diversity among Entamoeba histolytica and Entamoeba dispar Strains in Gastrointestinal Disorder Patients in Tehran, Iran

Since the first description of Amebiasis, we still do not have a proper answer to the question of why disease and symptoms develop in only 5 to 10% of those infected with E. histolytica. It has been speculated that a spectrum of virulence levels among the E. histolytica strains contribute to the outcome of amebic infection. In this study, beside determination of prevalence rate of E.histolytica and E.dispar in gastrointestinal disorder patients, genetic diversity in non-coding locus 1-2 was investigated to identify genetic differentiation of Entamoeba in positive isolates.

A total of 1700 stool samples were checked from patients referred to clinical laboratories affiliated with Shahid Beheshti Medical University samples were examined by direct and formalin detergent methods. Twenty seven cases of E. histolytica/E. dispar were detected and total genomic DNA was extracted from stool samples. E. histolytica/E. dispar complex were determined by PCR with two sets of species-specific primers from locus 1-2 gene. The purified PCR products were sequenced and the results were compared with known E. histolytica and E. dispar sequenced data.

PCR for locus 1-2 gene amplified a fragment of about 430 bp in 21 out of 27 samples and was identified as E. dispar. One isolate showed a band of about 340 bp and was identified as E. histolytica. PCR were negative in five samples which were discarded. With PCR and sequencing of the PCR products a reliable genetic diversity in size, number and position of the repeat units were seen among the Iranian E. dispar isolates in locus 1-2 gene.

Eight new E. dispar genotypes were found in this study and submitted to the GenBank/EMBL/DDBJ. The only Iranian E. histolytica isolate (NH1 E.h IR) was completely similar with the KU2 (Accession No. AB075706) strain reported from Japan.