Flowcytometric assessment of the effect of drugs on Giardia lamblia trophozoites in vitro.

The effect of albendazole, vincristine and metronidazole on the adherence, morphology, cell cycle and viability of Giardia lamblia trophozoites was evaluated. Albendazole rendered the trophozoites unable to attach which is a prerequisite for establishment of Giardia infection. The adherence assay showed that albendazole caused the detachment of trophozoites at a significantly lower concentration (0.1 microg/ml) as compared to metronidazole and vincristine (40 and 60 microg/ml, respectively) in the time period of 9 h. However, at the higher concentration (10 microg/ml) albendazole caused the similar effect within the time period of 3 h. The microscopic studies revealed that albendazole brought about gross morphological changes in G. lamblia, i.e., rounding of trophozoites and disruption of ventral adhesive disc along with vacuolation in cytoplasm. Metronidazole caused the ballooning of cytoplasm and induced the most lethal effect on trophozoites (8.17% viability) as compared to vincristine and albendazole (72.13 and 65.49% viability) as shown by flowcytometric analysis. Further, the flowcytometric findings indicated that the three drugs led to the arrest of growth of trophozoites at different stages of cell cycle. Albendazole and vincristine interfered with the formation of spindle/basal body microtubules thereby arresting the cell cycle in G2 + M phase whereas metronidazole arrested the growth in S-phase by inhibiting the DNA segregation and cell division. Hence, flowcytometry has been usefully employed to study the effect of drugs on viability and DNA of G. lamblia trophozoites in the present study.