Visual Detection of Leishmania Donovani and Leptomonas Seymouri in Co–Infected Samples by Their Specific DNA Biomarker and Gold Nanoparticle

Visceral leishmaniasis (VL) is a fatal tropical disease that often relapses in apparently recovered patients as post kalaazar dermal leishmaniasis (PKDL) in Indian subcontinent. Recently, the co-infection of Leishmania donovani and another tripanosmatid, Leptomonas seymouri has been reported in VL and PKDL in this region. The coexistence of Leishmania imposter, Leptomonas in the clinical isolates and its follow up cultures has been challenging in immunological and vaccine development research against leishmaniasis, where maintenance of pure Leishmania culture is a prerequisite. The impact of this newly observed parasitic co-habitation in diagnosis and management of VL and PKDL is yet to be ascertained. However, an early detection of this emerging co-infection has become intriguing for research and medical management of the disease. Internal transcribed spacer-1 (ITS-1), in which Leishmania and Leptomonas differ in sequences, were used as the specific markers in the current assay. The color of gold nanoparticle visually got changed as target DNA isolated from either of the species interacted with designed, species-specific oligonucleotide probes added externally. The current colorimetric assay to detect the co-infection of Leishmania and Leptomonas is a robust, sensitive, high throughput, low cost and rapid method requiring no sophisticated instruments.