Cryopreservation of Trichomonas vaginalis: a trial of using four different cryoprotectants

To reach the maximum survival rate of Trichomonas vaginalis after cryopreservation, four substances: dimethylsulphoxide (DMSO), glycerol, egg yolk and horse serum were used as cryoprotectants. T. vaginalis trophozoites, in the logarithmic phase, cultured on TYM-S medium were used. Rapid and slow freezing schedules were followed. Examinations for viable organisms were done after a month duration in liquid nitrogen. Immediate and delayed thawing were tried. Viability scores depended on the presence of live organisms in the thawed parasite suspensions determined by the presence of motile trophozoites under microscopic examination, by dye uptake and by re-suspension of the organisms in fresh TYM-S and watching for parasite growth and multiplication. Rapid freezing protocol failed to cryopreserve T. vaginalis with any cryoprotectant. DMSO was superior to glycerol especially in 10% conc. by slow freezing. Viable organisms were more when the suspensions were immediately thawed without delay.