Phylogenetic analysis and antimony resistance of Leishmania major isolated from humans and rodents

Cutaneous Leishmaniasis (CL) is one of the world's neglected diseases which is caused by Leishmania spp. The aim of this study was to assess molecular profile and antimony resistance of Leishmania isolated from human and rodent hosts. Samples were collected from suspected CL patients referred to health centres and wild rodent's traps in Gonbad-e-Qabus region, north-eastern Iran. Smears were subjected to PCR-RFLP to identify Leishmania species. In addition, ITS1-PCR products were sequenced for phylogenetic analysis. Clinical isolates and rodent samples were subjected to MTT assay to determine IC50 values and in vitro susceptibilities. Expression levels of antimony resistance-related genes were determined in CL isolates. Out of 1,949 suspected patients with CL and 148 rodents, 1,704 (87.4%) and 6 (4.05%) were positive with direct smear, respectively. Digestion patterns of BusRI (HaeIII) endonuclease enzyme were similar to what expected for Leishmania major. Phylogenetic analysis revealed that the highest interspecies similarity was found between current L. major sequences with L. major obtained from Russia and Uzbekistan. Out of 20 L. major samples tested, 13 (65%) were resistant to meglumine antimoniate (MA) treatment, with an activity index (AI) exceeding 4. The remaining 7 samples (35%) responded to MA treatment and were classified as sensitive isolates, with a confirmed sensitive phenotype based on their AI values. The comparison expression analysis of three major antimony resistance-associated genes in unresponsive clinical isolates demonstrated significant fold changes for TDR1 (4.78-fold), AQP1 (1.3-fold), and γ-GCS (1.17-fold) genes (P < 0.05). Herein, we demonstrate genetic diversity and antimony resistance of L. major isolated from human and reservoir hosts in north-eastern Iran, which could be the basis for planning future control strategies.