title: Evidence of a drug-specific impact of experimentally selected paromomycin and miltefosine resistance on parasite fitness in Leishmania infantum.
abstract: Although miltefosine and paromomycin were only recently introduced to treat visceral leishmaniasis, increasing numbers of miltefosine treatment failures and occasional primary resistance to both drugs have been reported. Understanding alterations in parasite behaviour linked to drug resistance is essential to assess the propensity for emergence and spread of resistant strains, particularly since a positive effect on fitness has been reported for antimony-resistant parasites. This laboratory study compared the fitness of a drug-susceptible parent WT clinical Leishmania infantum isolate (MHOM/FR/96/LEM3323) and derived miltefosine and paromomycin drug-resistant lines that were experimentally selected at the intracellular amastigote level.
  
  
  
  Parasite fitness of WT, paromomycin-resistant and miltefosine-resistant strains, in vitro and in vivo parasite growth, metacyclogenesis, infectivity and macrophage stress responses were comparatively evaluated.
  
  
  
  No significant differences in promastigote fitness were noted between the WT and paromomycin-resistant strain, while clear benefits could be demonstrated for paromomycin-resistant amastigotes in terms of enhanced in vitro and in vivo growth potential and intracellular stress response. The miltefosine-resistant phenotype showed incomplete promastigote metacyclogenesis, decreased intracellular growth and weakened stress response, revealing a reduced fitness compared with WT parent parasites.
  
  
  
  The rapid selection and fitness advantages of paromomycin-resistant amastigotes endorse the current use of paromomycin in combination therapy. Although a reduced fitness of miltefosine-resistant strains may explain the difficulty of miltefosine resistance selection in vitro, the growing number of miltefosine treatment failures in the field still requires further exploratory research.
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Hendrickx
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Beyers
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Mondelaers
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Eberhardt
authors.affiliation: Laboratoire de Parasitologie-Mycologie et Centre National de Référence des Leishmanioses, Centre Hospitalier Universitaire et Université de Montpellier, Montpellier, France.
authors.forename: L
authors.initials: L
authors.lastname: Lachaud
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Delputte
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Cos
authors.affiliation: Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium louis.maes@uantwerpen.be.
authors.forename: L
authors.initials: L
authors.lastname: Maes
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D004195:Disease Models, Animal; D004351:Drug Resistance; D005260:Female; D006801:Humans; D018314:Leishmania infantum / Q000187:drug effects* / Q000472:pathogenicity / Q000502:physiology; D007898:Leishmaniasis, Visceral / Q000469:parasitology / Q000473:pathology; D008807:Mice, Inbred BALB C; D010303:Paromomycin / Q000494:pharmacology*; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D012641:Selection, Genetic; D014774:Virulence
chemical_list: D000981:Antiprotozoal Agents; D010767:Phosphorylcholine; C039128:miltefosine; D010303:Paromomycin