title: Lack of correlation between the promastigote back-transformation assay and miltefosine treatment outcome.
abstract: OBJECTIVE
  Widespread antimony resistance in the Indian subcontinent has enforced a therapy shift in visceral leishmaniasis treatment primarily towards miltefosine and secondarily also towards paromomycin. In vitro selection of miltefosine resistance in Leishmania donovani turned out to be quite challenging. Although no increase in IC50 was detected in the standard intracellular amastigote susceptibility assay, promastigote back-transformation remained positive at high miltefosine concentrations, suggesting a more 'resistant' phenotype. This observation was explored in a large set of Nepalese clinical isolates from miltefosine cure and relapse patients to assess its predictive value for patient treatment outcome.
  
  
  METHODS
  The predictive value of the promastigote back-transformation for treatment outcome of a set of Nepalese L. donovani field isolates (n = 17) derived from miltefosine cure and relapse patients was compared with the standard susceptibility assays on promastigotes and intracellular amastigotes.
  
  
  RESULTS
  In-depth phenotypic analysis of the clinical isolates revealed no correlation between the different susceptibility assays, nor any clear link to the actual treatment outcome. In addition, the clinical isolates proved to be phenotypically heterogeneous, as reflected by the large variation in drug susceptibility among the established clones.
  
  
  CONCLUSIONS
  This in vitro laboratory study shows that miltefosine treatment outcome is not necessarily exclusively linked with the susceptibility profile of pre-treatment isolates, as determined in standard susceptibility assays. The true nature of miltefosine treatment failures still remains ill defined.
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Hendrickx
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Eberhardt
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Mondelaers
authors.affiliation: Medical Department, BP Koirala Institute of Health Sciences, Dharan, Nepal.
authors.forename: S
authors.initials: S
authors.lastname: Rijal
authors.affiliation: Medical Department, BP Koirala Institute of Health Sciences, Dharan, Nepal.
authors.forename: N R
authors.initials: NR
authors.lastname: Bhattarai
authors.affiliation: Department of Protozoology, Institute of Tropical Medicine Antwerp, Antwerp, Belgium.
authors.forename: J C
authors.initials: JC
authors.lastname: Dujardin
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Delputte
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Cos
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, Antwerp, Belgium louis.maes@uantwerpen.be.
authors.forename: L
authors.initials: L
authors.lastname: Maes
mesh_terms: D000981:Antiprotozoal Agents / Q000494:pharmacology / Q000627:therapeutic use*; D004351:Drug Resistance; D006801:Humans; D007893:Leishmania donovani / Q000187:drug effects* / Q000502:physiology*; D007898:Leishmaniasis, Visceral / Q000188:drug therapy* / Q000469:parasitology*; D009390:Nepal; D021261:Parasitic Sensitivity Tests; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D012008:Recurrence; D016896:Treatment Outcome
chemical_list: D000981:Antiprotozoal Agents; D010767:Phosphorylcholine; C039128:miltefosine