JAC Advance Access originally published online on March 13, 2008
Journal of Antimicrobial Chemotherapy 2008 61(6):1319-1327; doi:10.1093/jac/dkn092
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Original research |
Persistence of PCR-positive tissue in benznidazole-treated mice with negative blood parasitological and serological tests in dual infections with Trypanosoma cruzi stocks from different genotypes
1 Núcleo de Pesquisas em Ciências Biológicas (NUPEB), Instituto de Ciências Exatas e Biológicas (ICEB), Ouro Preto, MG, Brazil 2 Departamento de Análises Clínicas, Escola de Farmácia, Universidade Federal de Ouro Preto, Rua Costa Sena, 171, 35 400-000 Ouro Preto, MG, Brazil 3 Instituto René Rachou, FIOCRUZ, Belo Horizonte, MG, Brazil 4 Departamento de Ciências Biológicas, ICEB, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil 5 Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, UFMG, Belo Horizonte, MG, Brazil
Received 16 November 2007; returned 1 January 2008; revised 28 January 2008; accepted 12 February 2008
* Correspondence address. Núcleo de Pesquisas em Ciências Biológicas—Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Campus Universitário, Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil. Tel/Fax: +55-31-3559-1680; E-mail: helen{at}nupeb.ufop.br
Objectives: To assess different methodologies to better define an early post-therapeutic cure criterion after benznidazole treatment in BALB/c mice following mixed infection with dual Trypanosoma cruzi genotypes.
Methods: According to the classical cure criteria, animals were classified as treated not cured (TNC = 76.4%), treated cured (TC = 12.5%) and dissociated (DIS = 11.1%) using parasitological [fresh blood examination (FBE), blood culture (BC) and blood PCR] and serological methods [conventional serology (CS-ELISA) and non-conventional serology (NCS-FC-ALTA)]. Tissues were also evaluated by PCR.
Results: FBE was able to detect patent parasitaemia in only 18.1% of TNC and therapeutic failure was detected in 79.1% and 97.2% of TNC by BC and blood PCR, respectively. CS-ELISA should not be used before 3 months after treatment since it may lead to false-negative results. At 3 months after treatment with benznidazole, NCS-FC-ALTA was more efficient for categorizing the groups of treated mice. In the TNC group, although a decreased frequency of PCR-positive tissue was observed in several host tissues, increased positivity was also observed, despite the T. cruzi genotype combination. All TC animals presented at least two positive tissue-PCR results.
Conclusions: Our results confirm that NSC-FC-ALTA and blood PCR are the most suitable methods to early detect therapeutic failure in acute murine T. cruzi infection. Additionally, our data show that BC positivity is highly dependent upon the T. cruzi genotype combination. Moreover, our findings demonstrated that PCR tests performed on tissues from animals considered cured after benznidazole treatment still detected T. cruzi DNA, most probably indicating residual infection.
Keywords: mixed infection , genetic diversity , cure control , murine model