Abstract: Objective To observe the effect of different cryoprotective agents and temperature factors on the viability of Blastocystis hominis so as to explore the ideal method for preservation of B. hominis. Methods B. hominis agents were obtained from a patient′s fecal specimen. Having washed by normal saline and divided into tubes, the samples were cryopreserved in -20 ℃ refrigerator or in -l96 ℃ liquid nitrogen with 10% DMSO, 40% glycerol and 15% ethylene glycol respectively. The thawed B. hominis agents were then used for culture. By trypan blue staining and microscopy, the viability and proliferation of those resuscitative cells were investigated. Results B. hominis survived for 3 weeks at 18 ℃-20 ℃ while less than 1 week at 4 ℃-6 ℃. When stored in -20 ℃ refrigerator or liquid nitrogen with cryoprotective agents, they survived for more than 3 months. The cryopreservation with 40% glycerol at -196 ℃ for 6 months resulted in 41.7% viability of the revivified cells. Cleavage cells were easily observed after culturing for 72 hours. Conclusion Preserving B. hominis in liquid nitrogen with 40% glycerol is an optimal cryopreservation protocol.

Key words: Blastocystis hominis, Preservation, Temperature