Trypanosoma cruzi : sensitivity of the polymerase chain reaction for detecting the parasite in the blood of mice infected with different clonal genotypes.

The polymerase chain reaction showed high sensitivity for detecting Trypanosoma cruzi in the blood of mice, independent of clonal genotype (19, 20?T. cruzi I; 32, 39?T. cruzi II) or phase of the infection (acute or chronic)

Differential parasitological, molecular, and serological detection of Trypanosoma cruzi I, II, and IV in blood of experimentally infected mice.

Trypanosoma cruzi is the etiological agent of American trypanosomiasis (Chagas' disease), which affects 6 e7 million people worldwide, mainly in Latin America. It presents great genetic and biological variability that plays an important role in the clinical and epidemiological features of the disease. Our working hypothesis is that the genetic diversity of T. cruzi has an important impact on detection of the parasite using diagnostic techniques. The present study evaluated the diagnostic performance of parasitological, molecular, and serological techniques for detecting 27 strains of T. cruzi that belonged to discrete typing units (DTUs) TcI (11 strains), TcII (four strains), and TcIV (12 strains) that were obtained from different hosts in the states of Amazonas and Paran a, Brazil. Blood samples were taken from experimentally infected mice and analyzed by fresh blood examination, hemoculture in Liver Infusion Tryptose (LIT) medium, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA). Polymerase chain reaction presented the best detection of TcI, with 80.4% positivity. For all of the detection methods, the animals that were inoculated with TcII presented the highest positivity rates (94.1e100%). ELISA that was performed 7 months after inoculation presented a higher detection ability (95.4%) for TcIV. Intra-DTU comparisons showed that the reproducibility of the majority of the results that were obtained with the different methods was weak for TcI and good for TcII and TcIV. Our data indicate that the detection capability of different techniques varies with the DTUs of the parasites in mammalian blood. The implications of these findings with regard to the diagnosis of human T. cruzi infection are discussed

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

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