Abstract
There is no simple explanation for the varied spectrum of clinical disease produced by Giardia. This may partly relate to strain variation but as yet no virulence factors have been identified. We have characterised 12 human Giardia isolates from UK, USA and travellers to Asia and 2 isolates from animals by (l) [35s]-methionine radiolabelling profiles, (2) isoenzyme analysis, (3) heat-shock proteins and (4) DNA analysis by RFLP. [35S]methionine profiles resolved by SDS-PAGE enabled isolates to be separated into 5 groups, isoenzyme analysis into three groups according to malic enzyme isoenzymes (but not G6PD or hexokinase) and RFLP analysis with Hind III and a cloned Giardia DNA probe revealed polymorphisms in 3 isolates, 2 of which also exhibited the malic enzyme zymodeme differences. Heat shock proteins (94, 81, 70, 30kDa) were demonstrated in all Giardia isolates but did not discriminate between them. We have used these approaches to study Giardia isolate variation in a patient with immunodeficiency and chronic giardiasis and have shown that during several unsuccessful treatments with metronidazole both the phenotypic ([35S]-methionine profile, isoenzymes) and genotypic (RFLP) characteristics of the isolate changed, probably indicating selection of a resistant clone since sensitivity to metronidazole decreased >40-fold during the 3 month study. Thus, these techniques can identify phenotypic and genotypic differences between Giardia isolates and may prove useful typing systems for identification of virulence factors.
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Farthing, M., Butcher, P., Cevallos, A. et al. PHENOTYPIC AND GENOTYPIC VARIATION IN GIARDIA LAMBLIA. Pediatr Res 27, 537 (1990). https://doi.org/10.1203/00006450-199005000-00073
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DOI: https://doi.org/10.1203/00006450-199005000-00073