In vitro phenotype of reduced susceptibility to artemisinin in Plasmodium falciparum isolates from western Cambodia
Benoît Witkowski, K. Sokunmalis, S. Kim, C. Pheaktra, K. Sopheakvatey, Nimol Kloeung, Nimol Khim, S. Duong, Rithea Leang, Pascal Ringwald, Arjen M. Dondorp, Rupam Tripura, Antoine Berry, Françoise Benoit‐Vical, Jean-Christophe Barale, Odile Mercereau‐Puijalon, Didier Ménard · International Journal of Infectious Diseases · 2012
Background: The increased resistance of Plasmodium falciparum to artemisinin derivatives in Western Cambodia was described through a markedly slower parasite clearance in patients and high failure rates in the next weeks after the treatment, at a time where we have no methodology to study it in vitro and we have no predictive molecular or biochemical marker is of major concern. Methods: Based on physiologically relevant conditions (in time and in concentration), we propose, here, a new in vitro assay using 6-hours pulse exposure of 700 nM of dihydroartemisinin on ring stages parasites from Pailin (artemisinin-resistant area, western Cambodia) and Ratanakiri (artemisinin-susceptible area, Eastern Cambodia). Results: Parasites viability determined 66-hours post-exposure was significantly higher for parasites from Pailin (mean = 11.9% ± 8.7%, range: 2.9%-31.4%) compared to those from Ratanakiri (mean = 0.9% ± 0.7%, range: 0.06%-2.2%). In addition, we also demonstrated for the first time in field isolates that resistance to artemisinin is mediated by cell growth arrest (quiescence or dormancy) and found positive correlations with parasite clearance time in patients treated by artesunate monotherapy. Conclusion: Compared to the isotopic 48-hours test, the 6 hours exposure to 700 nM DHA viability assay provides a relevant in vitro phenotype to discriminate susceptibility to artemisinin drugs.