Infectivity of Giardia duodenalis Assemblages A and E for the gerbil and axenisation of duodenal trophozoites

Establishing in vitro cultures of Giardia duodenalis trophozoites from faecal cysts remains very difficult due to poor excystation and bacterial contamination. This study investigated an alternative approach starting from duodenal trophozoites of gerbils that were artificially infected with field isolates from humans (Assemblages A and B) and cattle (Assemblage E and mixed E/A). Gerbil infection was successful for Assemblages A (1/1) and B (1/3) from humans, and for E (1/2) and mixed E/A (6/6) from cattle. Despite the fact that some isolates subsequently failed or were difficult to establish in vitro, several Assemblage A and Assemblage E in vitro trophozoite cultures were successful, however, subsequent cloning required adaptation of the standard TYI-S-33 medium whereby different medium supplements were required for promoting growth. Excess of l-cysteine (2 mg/ml) and ascorbic acid (0.2 mg/ml) supported cloning of Assemblage A, while l-glutathione (7.8 mg/ml) was required for Assemblage E. This is a first description of in vitro axenisation of Assemblage E trophozoites from cattle.

In vitro axenic trophozoite cultures of Giardia duodenalis were obtained from faecal cysts of man and cattle after prior recovery from the small intestine of artificially infected gerbils. Genotyping glutamate dehydrogenase (gdh), β-giardin and the triosephosphate isomerase (tpi) genes revealed the presence of Assemblages A and E trophozoites of which pure cloned cultures were obtained. This is the first description of an established trophozoite in vitro culture of Assemblage E from cattle.Figure optionsDownload as PowerPoint slide