Introduction

Leishmania is protozoa belonging to the Family Trypanosomatidae of the Order Kinetoplastida (Lainson and Shaw, 1987). These protozoans are parasites responsible for leishmaniasis. The parasites are transmitted to vertebrate hosts by the bite of female sand flies (Bates, 2007). The parasites have dimorphic life cycle, including an intracellular amastigote form and a promastigote form. The amastigote is characterized by a round or ovoid shape. The immotile amastigote multiplies in the cytoplasm of macrophages of vertebrate hosts. The promastigote form is characterized by a spindle-shape. This form uses a flagellum for motility and is found in female sand fly (Bates, 2007; Kato et al., 2010). Leishmaniasis occurs in tropical and subtropical areas and southern Europe (Steverding, 2017). Leishmaniasis is classified into the Old World and New World leishmaniasis. Old World leishmaniasis is caused by the subgenus Leishmania, which is found in Africa, Asia, the Middle East, the Mediterranean, and India. New World leishmaniasis is found in Central and South America and is caused by the L. mexicana complex and all species of the subgenus Viannia (Maltezou, 2010). There are three main clinical forms of the disease, including visceral, cutaneous, and mucocutaneous leishmaniasis (Lainson and Shaw, 1987; Maltezou, 2010). Clinical forms and treatment depend on the Leishmania species (Mouri et al., 2014). In Thailand, indigenous leishmaniasis is an emerging disease described in recent years. The disease was reported in northern, central and southern regions of Thailand (Maharom et al., 2008). Two major Leishmania species L. martiniquensis and L. siamensis (L. orientalis n. sp.) (Sukmee et al., 2008; Suankratay et al., 2010; Bualert et al., 2012; Chusri et al., 2012; Phumee et al., 2013; Noppakun et al., 2014; Osatakul et al., 2014; Phumee et al., 2014; Pothirat et al., 2014; Chiewchanvit et al., 2015; Siriyasatien et al., 2016; Jariyapan et al., 2018) were reported in Thailand. Several drugs are effective for the treatment of leishmaniasis, including pentavalent antimonials, amphotericin B deoxycholate, lipid formulations of amphotericin B, miltefosine, paromomycin, pentamidine and sodium stibogluconate; however, these drugs exhibit different modes of action, adverse effects, costs, and routes of administration (Croft and Brazil, 1982; Singh and Sivakumar, 2004; Singh, 2006; Morizot et al., 2016). Currently, several reports described the increasing drug resistance in many Leishmania species (Croft et al., 2006; Mohapatra, 2014). However, the level of resistance varies according to the Leishmania species, strain, stages of Leishmania and the distribution and frequency of resistance to anti-leishmanial drugs are unknown. The variation in intrinsic sensitivity among some Leishmania species to several drugs depends on genetic, molecular, and biochemical variations. In Thailand, amphotericin B is the only effective drug available for the treatment of leishmaniasis; however, some patients developed relapsed leishmaniasis after receiving amphotericin B treatment (Suankratay et al., 2010; Chusri et al., 2012; Phumee et al., 2013; Phumee et al., 2014; Pothirat et al., 2014; Siriyasatien et al., 2016). Moreover, the efficacy of amphotericin B and other antileishmanial drugs against L. martiniquensis has never been evaluated. Therefore, in this study, we sought to determine the efficacy of anti-leishmanial drugs against various strains of L. martiniquensis isolated from Thai patients using colorimetric assays. The resazurin-based assay PrestoBlue™ Cell Viability Reagent was used because it is a non-toxic, water soluble, redox-sensitive dye. Data obtained from this study may potentially improve the treatment of leishmaniasis caused by L. martiniquensis in Thailand.