In vivo susceptibility to benznidazole of Trypanosoma cruzi strains from the western Brazilian Amazon.

Abstract

objective To assess the susceptibility of Trypanosoma cruzi strains from Amazon to benznidazole.methods We studied 23 strains of T. cruzi obtained from humans in the acute phase of Chagasdisease, triatomines and marsupials in the state of Amazonas and from chronic patients andtriatomines in the state of Parana´, Brazil. The strains were classified as TcI (6), TcII (4) and TcIV(13). For each strain, 20 Swiss mice were inoculated: 10 were treated orally with benznidazole100 mg/kg/day (TBZ group) for 20 consecutive days and 10 comprised the untreated control group(NT). Fresh blood examination, haemoculture (HC), PCR, and ELISA were used to monitor the cure.results The overall cure rate was 60.5% (109/180 mice) and varied widely among strains. Thestrains were classified as resistant, partially resistant or susceptible to benznidazole, irrespective ofdiscrete typing units (DTUs), geographical origin or host. However, the TcI strains from Amazonaswere significantly ( P = 0.028) more sensitive to benznidazole than the TcI strains from Parana´. Thenumber of parasitological, molecular and serological parameters that were significantly reduced bybenznidazole treatment also varied among the DTUs; the TBZ group of mice inoculated with TcIVstrains showed more reductions (8/9) than those with TcI and TcII strains.conclusions Benznidazole resistance was observed among natural populations of the parasite inthe Amazon, even in those never exposed to the drug.