The molecular characterization of clinical isolates from Indian Kala-azar patients by MLEE and RAPD-PCR

Abstract

Background: Kala-azar is a serious health problem in India. The situation has worsened further due to the occurrence of cases unresponsive to antimonials. About 30-50% patients do not respond to the prevailing regimen of antimonials. The etiological agent for Indian kala-azar has long been known to be Leishmania donovani. Recently, in a somewhat startling report, it was claimed that L. tropica causes nearly 25% of current kala-azar cases in India. It was also suggested that this might be in some way related to the unresponsiveness to pentavalent antimonials in the field. Material/Methods: Two independent molecular characterization techniques, multilocus enzyme electrophoresis (MLEE) and RAPD-PCR, were employed to analyze 15 clinical isolates from confirmed Indian kala-azar patients collected from the eastern part of the country over a period of nearly 20 years. The collection included six Sb⁵⁺-unresponsive and one PKDL case. Results: Our observations strongly suggest that all the clinical isolates, including the antimony (Sb⁵⁺)-unresponsive and PKDL ones, we studied were identical to the WHO reference strain (DD8) for Leishmania donovani by both the above methods and no strain variation might have occurred in two major epidemic and inter-epidemic periods. We also observed that none of the Sb⁵⁺-unresponsive stains we analyzed was related to L. tropica. Conclusions: We conclude that L. donovani may be the causal agent for Indian kala-azar and that L. tropica is most likely not an etiological agent for Indian Kala-azar cases that are unresponsive to antimonials.