Rapid identification of causative species in patients with Old World leishmaniasis

Conventional methods for the identification of species of Leishmania parasite causing infections have limitations. By using a DNA-based alternative, the present study tries to develop a new tool for this purpose. Thirty-three patients living in Marseilles (in the south of France) were suffering from visceral or cutaneous leishmaniasis. DNA of the parasite in clinical samples (bone marrow, peripheral blood, or skin) from these patients were amplified by PCR and were directly sequenced. The sequences observed were compared to these of 30 strains of the genus causing Old World leishmaniasis collected in Europe, Africa, or Asia. In the analysis of the sequences of the strains, two different sequence patterns for Leishmania infantum, one sequence for Leishmania donovani, one sequence for Leishmania major, two sequences for Leishmania tropica, and one sequence for Leishmania aethiopica were obtained. Four sequences were observed among the strains from the patients: one was similar to the sequence for the L. major strains, two were identical to the sequences for the L. infantum strains, and the last sequence was not observed within the strains but had a high degree of homology with the sequences of the L. infantum and L. donovani strains. The L. infantum strains from all immunocompetent patients had the same sequence. The L. infantum strains from immunodeficient patients suffering from visceral leishmaniasis had three different sequences. This fact might signify that some variants of L. infantum acquire pathogenicity exclusively in immunocompromised patients. To dispense with the sequencing step, a restriction assay with HaeIII was used. Some restriction patterns might support genetic exchanges in members of the genus Leishmania.