Autochthonous
leishmaniasis caused by Leishmania martiniquensis cases in Thailand have dramatically increased in the recent years. L. martiniquensis
infection primarily occurs in immunocompromised patients, especially
AIDS patients. In Thailand,
amphotericin B is the only
drug available for
leishmaniasis treatment, and some patients relapse after
amphotericin B therapy. Moreover, the efficacy of anti-leishmanial drugs against L. martiniquensis has not been evaluated to date. In this study, we determined the efficacy of various anti-leishmanial drugs against the promastigote and intracellular amastigote stages of L. martiniquensis using a colorimetric assay. Two strains (CU1 and CU1R1) were isolated from
leishmaniasis HIV co-infected patient from Songkhla province, southern Thailand. The CU1 strain was isolated from the patient in 2011, and CU1R1 was isolated from the same patient in 2013, when he was diagnosed as relapse
leishmaniasis. The third strain (LSCM1) used in this study has been isolated from immunocompetent patient from Lamphun province, northern Thailand. All strains were identified as L. martiniquensis by sequencing of
ribosomal RNA ITS-1 and large subunit of
RNA polymerase II gene. Bioassays have been conducted both with promastigote and intracellular amastigote stages of the parasite. All L. martiniquensis strains have been tested against
amphotericin B,
miltefosine and
pentamidine to determine the efficacy of the drugs against the parasite by using a PrestoBlue. The efficacy of
miltefosine and
pentamidine exhibit no significant difference between each stage of L. martiniquensis among all strains. Surprisingly, the promastigote and intracellular amastigote of the CU1R1 isolate, which was isolated from a relapsed patient after
amphotericin B treatment, exhibited a two-fold increased inhibitory concentration (IC50) against
amphotericin B compared with other strains, and the difference was statistically significant (p < 0.05). Moreover, intracellular amastigotes isolated from CU1R1 exhibited slightly increased susceptibility to
amphotericin B compared with the promastigote (p < 0.05). The result of this experiment is a scientific evident to support that in case of relapsed
leishmaniasis caused by L. martiniquensis, increasing dosage of
amphotericin B is essential. Moreover, this study also determined efficacy of other anti-leishmanial drugs for treatment the
leishmaniasis in Thailand in case of these drugs are available in the country and the clinicians should have alternative drugs for treatment
leishmaniasis in Thailand apart from
amphotericin B.