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.

Molecular identification of coproantigens of Cryptosporidium parvum compared to conventional staining techniques.

To compare the immunologic techniques to the conventional staining methods (mainly modified Ziehl Neelsen = MZN), 93 children (65 immunocompromised and 28 immunocompetent) potentially at risk of Cryptosporidium parvum were studied. Using MZN, a prevalence of 10.7% in diarrhoeic children was found. ELISA coproantigen and detection of 23 KDa band of immunoblotting by serum IgG were sensitive and specific. They gave 85.7% sensitivity, 100% specificity, 100% diagnostic accuracy, 100% positive predictive value and 98.9% negative predicttive value. ELISA detection of serum IgG gave 85.7% sensitivity, 97.7% specificity, 96.8% diagnostic accuracy, 75% positive predictive value and 98.9% negative predictive value. So, 23KDa band determined by ELISA is a valuable sensitive and specific mean of diagnosing cryptosporidiosis as this antigen is a consistent target of humoral immune response.