In vitro encystation of Blastocystis hominis: a kinetics and cytochemistry study.

The kinetics of in vitro encystation of Blastocystis hominis was studied over 9 days. The differentiation between trophic (TF) and cyst forms (CF) was determined by differential counts before and after treatment with distilled water. A cytochemistry study using acridine orange and Calcofluor white wet-mount preparations of CF was carried out. The growth curves of TF and CF were related because the decrease in TF was followed by an increase in CF, and vice versa. The maximum of CF counts was obtained on the 6th or 7th day. Using the differential acridine orange stain, two subpopulations of CF, yellow-orange fluorescent cells or precysts and green fluorescent cells or cysts, were detected and their curves were also related. CF was stained by Calcofluor white, which suggested the existence of beta-(1-4)-glycosyl residues in the wall cysts of B. hominis.