Molecular characterization of the Iranian isolates of Giardia lamblia: application of the glutamate dehydrogenase gene

This study was conducted to determine of molecular epidemiology of the Giardia lamblia by PCR-RFLP method in Tehran, capital of Iran. Thirty eight stool samples were randomly selected from 125 patients diagnosed with giardiasis using microscopy in Tehran. DNA extraction of some samples were performed by phenol/chloroform/isoamyl alcohol method and to raise the sen sitivity of the PCR assay, the genomic DNA of the others were extracted using glass beads and the QIAamp Stool Mini Kit in order to effectively remove the PCR inhibitors. A single step PCR-RFLP assay, targeting the glutamate dehydro genase (gdh) locus, was used to differentiate within and between assemblages A and B that have been found in humans. Of the 38 isolates, 33 samples (87%) were found as G. lamblia (genotype AII), 3 (7.8%) belonged to assemblage B, genotype BIII, the mixed of genotype AII and B were detected only in two samples (5.2%). PCR-RFLP is a sensitive and powerful analytical tool that allows effective genotype discrimination within and between assemblages at targeting gdh gene, and makes it possible to identify the presence of mixed genotypes. Our data sug gest that there is an anthroponotic origin of the infection route, assemblage A group II, in Tehran so it seems that the main reservoir of Giardia infection is humans in the area studies.