in vitro culture and isoenzyme analysis of giardia lamblia

Rice & Schaefer method by Hamilton and Jackson, 1990), a high success rate
(71 %) was attained in the current work. The method however, involved a postinduction
incubation step in modified HSP medium. The excysted tropholoites
had to be subsequently transferred to TYI-S-33 medium for propagation and long
term in vitro maintenance. Later it became apparent that this was not suited for
the aim of propagation of viable cultures (as detailed in Chapter 5). therefore the
modified method of Hamilton & Jackson (1990) was abandoned.
The acid-pepsin method was better suited for fulfilment of the aims of the present
work. Furthermore, in their experiments, Kasprzak and Majewska (1985) showed
that although the percentage excystation of G.intestinalis and G.muris cysts
induced by using the TYI-S-33 as the excystment solution is reduced, the resulting
yields of tropholoites are greater. The two media (Acid Pepsin induction and TYI­
S-33 excystment) were subsequently employed in the current study. Using this
method, successful excystation was also achieved, however a comparatively
lower success rate was attained.
Excystation is dependent, among other factors upon viability of the cysts. In the
current work, viability was assessed by the eosin exclusion method. Although
excystation is in itself a measure of viability, the dye exclusion method consistently
revealed higher levels of viability than that resulting from any of the excystation
experiments (Appendices 3,4 & 5). The two processes therefore are not
comparable. However it must be noted that various factors such as the ability of in
vitro methods to induce successful excystation must be considered in interpreting
these results. On the other hand, the ability of cysts to exclude dye appears to be
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