Resistance to treatment in Kala-azar: Speciation of isolates from northeast India

Kala-azar in India is becoming increasingly difficult to treat, which may b e due to the presence of species other than Leishmania donovani; Leishmania tropica was reported to cause the same clinical syndrome in the area. Over the past 3 years, we have collected samples from 241 patients with viscera l leishmaniasis from across the region. Of the 189 isolates that grew on di phasic medium, 159 were successfully transferred to liquid medium for typin g. Clinically, 80% of these were resistant to antimony. Lipophosphoglycan-s pecific monoclonal antibodies were used to distinguish the 2 species by agg lutination of promastigotes; all 159 were shown to be L. donovani. Eighty-t hree isolates were confirmed to be L. donovani by isoenzyme analysis, by am plification of kinetoplast DNA, or both, in comparison with multiple refere nce strains; none were L. tropica. Thus, the rising incidence of clinical r esistance to treatment is unlikely to be due to a different species causing kala-azar in north Bihar.