Variation in Susceptibility to Benznidazole in Isolates Derived from Trypanosoma cruzi Parental Strains

In this work, the susceptibility to benznidazole of two parental Trypanosoma cruzi strains, Colom-bian and Berenice-78, was compared to isolates obtained from dogs infected with these strains for several years. In order to evaluate the susceptibility to benznidazole two groups of mice were infected with one of five distinct populations isolated from dogs as well as the two parental strains of T. cruzi. The first group was treated with benznidazole during the acute phase and the second remained un-treated controls. The animals were considered cured when parasitological and serological tests re-mained persistently negative. Mice infected with the Colombian strain and its isolates Colombian (A and B) did not cure after treatment. On the other hand, all animals infected with Berenice-78 were cured by benznidazole treatment. However, 100%, 50 % and 70 % of cure rates were observed in animals infected with the isolates Berenice-78 B, C and D, respectively. No significant differences were observed in serological profile of infected control groups, with all animals presenting high antibody levels. However, the ELISA test showed differences in serological patterns between mice inoculated with the different T. cruzi isolates and treated with benznidazole. This variability was dependent on the T. cruzi population used and seemed to be associated with the level of resistance to benznidazole. Key words: chemotherapy- drug susceptibility- Trypanosoma cruzi- benznidazole Trypanosoma cruzi, the agent of Chagas dis-ease, exhibits considerable biological variability (Carneiro et al. 1991, Andrade & Magalhães 1997). Studies using cloned or uncloned populations, re-inforce the heterogeneity of the parasite and dem-onstrate that, in general, strains of T. cruzi are com-posed of subpopulations with distinct characteris