Detection of Leishmania donovani using ITS1-RFLP from positive and negative smear samples among clinically reported patients visiting University of Gondar Comprehensive Specialized Hospital.

backgroundVisceral leishmaniasis is caused by the Leishmania donovani species complex that can spread to internal organs and leading to death if not treated on time. Diagnosis of leishmaniasis is based on clinical signs and symptoms, microscopy, serological and molecular techniques. Because of a broad spectrum of diverse clinical manifestations and similarities of the responses to different species, identification to the species level is often difficult for the proper patient treatment and management. Therefore, the objective of this study was to evaluate the PCR- RFLP assay of the ITS1 region for identification of L. donovani species from clinical smear slide patient samples.

methodDNA extraction was performed on a total of 90 smear slide samples using phenol-chloroform method. The PCR detection limit was determined by L. donovani reference strain DNA. The ITS1 region was amplified at 320 bp using LITSR/L5.8S genus specific primers and then the ITS1-PCR products were subjected to RFLP assay for confirmation of L. donovani species using HaeIII restriction enzyme.

resultsOf the total samples ITS1-PCR revealed the true positive, false positive, true negative, and false negative results of 42 (46.7%), 6 (6.7%), 37 (41.1%) and 5 (5.6%), respectively. Considering microscopy as the gold standard, the sensitivity, specificity, positive predictive values, and negative predictive values of the ITS1- PCR technique was 89.4%, 86.0%, 87.5%, and 88.1% respectively. All ITS1-PCR positive clinical samples were confirmed as L. donovani species by PCR-RFLP patterns.

conclusionIn conclusion, the ITS1- RFLP method is highly sensitive and more specific for identification of L. donovani species in the smear negative clinical samples of visceral leishmaniasis patients. There is also significant association and degree of agreement between the two methods. For direct identification of L. donovani species from clinical samples, irrespective of genus and species level, PCR-RFLP is more recommendable than a microscope.