Introducing a simple and economical method to purify <i>Giardia lamblia</i> cysts

Abstract

Direct microscopic examination of stool to diagnosis giardiasis (wet mount) has low diagnostic value, but immunologic methods (like IFA and especially ELISA) that are based on the determination of parasite antigens in fecal samples (antigen detection) have relatively high sensitivity and specialty. To prepare anti-Giardia lamblia antibodies needed to design diagnostic kits as well as parasite culture and other molecular studies, we require purification of the parasite cysts. In this study, we designed a rapid, simple and inexpensive method to purify parasite cysts from fecal samples of the patients suffering from giardiasis. Initially, fecal samples that the presence of G. lamblia in them was affirmed by direct microscopic observation of cysts were subjected to various purification methods like one- and twophase sucrose gradient isolation, percoll-sucrose gradient isolation, and a modified two-phase method run by 0.85 and 1.5 M sucrose. The first procedure contained some contents of bacteria and small particles of feces. In the second and third procedure, bacteria were almost removed and the cysts were intact but the suspension contained some extras and cellulose particles. The recovery rate for modified two-phase method was 1.5 × 10⁴ cysts for each two grams of fecal sample. In this study, by using and comparing with the results of some other studies, we introduce and run a modified method that in fact is a mélange of them with some changes. So this method could be recommended as a fast, advantageous and simple method in purification of G. lamblia cysts.

Key words: Giardia lamblia, cyst, purification.