Giardia duodenalis is an intestinal flagellated protozoan and the common cause of
gastrointestinal diseases in human. This parasite can be seen in two different forms in its life cycle including as
cyst and trophozoite. Due to presence of resistant
cyst wall,
DNA extraction inhibitors along with artifact in stool specimens, this study was performed aiming to evaluate four methods for
DNA extraction from G. duodenalis
cysts. Seventy G. duodenalis positive stool specimens that were confirmed by light microscope were included in this study. All stool samples were concentrated using four layered discontinuous
sucrose flotation technique (0.5, 0.75, 1, and 1.5 M) and single-layered
sucrose solution (0.85 M). The isolated
cysts were then subjected to
DNA extraction by four methods. To remove the artifacts, the extracted
DNA were evaluated by PCR. The results of the present study showed the high level of optical density (OD) in the method I (P < 0.01) with the following steps; Giardia
cysts plus crushed cover glass were vortexed. Then, the samples were boiled and then followed by freeze-thaw cycles, yet this method yielded the lowest concentration. Furthermore, the highest concentration were observed in the method II (P <0.01) with the following steps; Giardia
cysts plus crushed cover glass and
TAE buffer were mixed and then shaken, followed by boiling. Based on the results of the present study, using crushed cover glass, boiling and freeze-thaw cycles can be effective in destruction of G. duodenalis
cyst wall and have enough efficiency for extracting
DNA from G. duodenalis
cysts.