In Vitro Benznidazole and Nifurtimox Susceptibility Profile of Trypanosoma cruzi Strains Belonging to Discrete Typing Units TcI, TcII, and TcV.

We ascertain the in vitro Benznidazole (BZN) and Nifurtimox (NFX) susceptibility pattern of epimastigotes, trypomastigotes, and amastigotes of 21 T. cruzi strains, from patients, reservoir, and triatomine bugs of various geographic origins. Using this panel of isolates, we compute the Epidemiological cut off value (COwt). Then, the frequency of the susceptible phenotype (Wild type) towards benznidazole (BZN) and nifurtimox (NFX) within this set of strains belonging to three discrete typing units (DTUs), TcI, TcII, and TcV, was deduced. We observed that the susceptibility status of individual T. cruzi isolates toward BZN and NFX is related to the genetic background and underlying factors that are probably related to the individual life trait history of each strain. Analyzing drug susceptibility in this conceptual framework would offer the possibility to evidence a link between isolates expressing a low susceptibility level (not wild-type) as defined by the COwt value and none-curative treatment. It will also permit us to track drug-resistant parasites in the T. cruzi population.

What pre-Columbian mummies could teach us about South American leishmaniases?

A recent report on the taxonomic profile of the human gut microbiome in pre-Columbian mummies (Santiago-Rodriguez et al. 2016) gives for the first time evidence of the presence of Leishmania DNA (sequences similar to Leishmania donovani according to the authors) that can be reminiscent of visceral leishmaniasis during the pre-Columbian era. It is commonly assumed that Leishmania infantum, the etiological agent of American visceral leishmaniasis (AVL) was introduced into the New World by the Iberian conquest. This finding is really surprising and must be put into perspective with what is known from an AVL epidemiological and historical point of view. Beside L. infantum, there are other species that are occasionally reported to cause AVL in the New World. Among these, L. colombiensis is present in the region of pre-Columbian mummies studied. Other explanations for these findings include a more ancient introduction of a visceral species of Leishmania from the Old World or the existence of a yet unidentified endemic species causing visceral leishmaniasis in South America. Unfortunately, very few molecular data are known about this very long pre-Columbian period concerning the circulating species of Leishmania and their diversity in America.