in vitro culture and isoenzyme analysis of giardia lamblia

5.5 DISCUSSION
In the present work, cultures were initiated from excystation of faecally derived
cysts, therefore parts of this discussion ~onsider the results in accordance with the
in vitro and in vivo culture findings.
Initiation of viable long-term cultures from in vitro excystation proved to be
impossible. Excystment and trophozoite survival were the two major factors that
governed successful attempts at in vitro cultivation of the organisms. Although
successful excystment was achieved in some cases, the individual levels of
excystation were low, and if successfully excysted, trophozoites survived for
several hours and subsequently died. Therefore, only short-term cultures were
established. While some authors reported successful establishment of viable
cultures from in vitro excystation of cysts (Bingham & Meyer, 1979; Isaac-Renton
et al., 1986; Meloni & Thompson, 1987; Meloni et al., 1988; Cedillo-Rivera et al.,
1989; AI-Tukhi et al., 1991), others, as in the present study experienced difficulty
in establishing cultures from in vitro excysted trophozoites (Isaac-Renton et al.,
1986; Kaur et al., 1986).
In the current study, apart from the scanty numbers of trophozoites that resulted
from low levels of excystation, contaminating faecal microrganisms played a
negative role in the failed attempts to establish cultures from in vitro excysted
cysts of faecal origin. Although a variety of antibiotics were used, a large
proportion of cultures was overwhelmed by faecal contaminants. This might be a
reflection of the wide distribution of resistant organisms in the local population
from which cysts were obtained. The combined effect of these factors made it
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