Introducing a simple and economical method to purify Giardia lamblia cysts

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