Intraspecies susceptibility of Leishmania (Viannia) braziliensis to antileishmanial drugs: Antimony resistance in human isolates from atypical lesions.

Leishmania (Viannia) braziliensis is the most common etiological agent of cutaneous and mucocutaneous leishmaniasis (MCL) in Latin America. An interesting aspect of the disease outcome caused by this species is the appearance of non-ulcerated atypical cutaneous leishmaniasis. Atypical (AT) lesions are often associated with therapeutic failure when treated with antimony(Sb)-based drugs. Refractory cases are not necessarily due to intrinsic parasite drug resistance. The status of in vitro drug susceptibility from L. braziliensis field isolates is less assessed than patient treatment outcome. In this work, L. braziliensis isolated from typical CL (6), MCL (1) and AT (3) lesions and vector (1) were tested for their susceptibility to amphotericin B (AmB), miltefosine (MIL), glucantime (GLU) and non-comercial meglumine antimoniate (MA). Overall, intracellular amastigotes of all isolates were sensitive to the tested antileishmanial drugs except AT lesions-derived strains 316, 330 and 340 that presented in vitro resistance against Sb-based drugs. Although susceptible to miltefosine - based on phenotypic screening - intramacrophagic quiescent amastigotes could restore infection. L. braziliensis promastigotes isolated from AT lesions also displayed 29% reduced capacity to infect human monocyte-derived macrophages when compared with parasites obtained from patients with typical lesions, MCL or from sand-fly. These data indicate differences in drug susceptibility and infectiveness among L. braziliensis isolated from patients exhibiting different types of lesions and highlight the importance of its characterization for drug response prediction outcome in clinical practice.