Prevalence and characterization of piperaquine, mefloquine and artemisinin derivatives triple-resistant Plasmodium falciparum in Cambodia

Background In early 2016, in Preah Vihear, Northern Cambodia, artesunate/mefloquine was used to cope with dihydroartemisinin/piperaquine-resistant Plasmodium falciparum parasites. Following this policy, P. falciparum strains harbouring molecular markers associated with artemisinin, piperaquine and mefloquine resistance have emerged. However, the lack of a viable alternative led Cambodia to adopt artesunate/mefloquine countrywide, raising concerns about a surge of triple-resistant P. falciparum strains. Objectives To assess the prevalence of triple-resistant parasites after artesunate/mefloquine implementation countrywide in Cambodia and to characterize their phenotype. Methods For this multicentric study, 846 samples were collected from 2016 to 2019. Genotyping of molecular markers associated with artemisinin, piperaquine and mefloquine resistance was coupled with phenotypic analyses. Results Only four triple-resistant P. falciparum isolates (0.47%) were identified during the study period. These parasites combined the pfk13 polymorphism with pfmdr1 amplification, pfpm2 amplification and/or pfcrt mutations. They showed significantly higher tolerance to artemisinin, piperaquine and mefloquine and also to the mefloquine and piperaquine combination. Conclusions The use of artesunate/mefloquine countrywide in Cambodia has not led to a massive increase of triple-resistant P. falciparum parasites. However, these parasites circulate in the population, and exhibit clear resistance to piperaquine, mefloquine and their combination in vitro. This study demonstrates that P. falciparum can adapt to more complex drug associations, which should be considered in future therapeutic designs.

Automated summary

The implementation of artesunate/mefloquine countrywide in Cambodia has not caused a significant increase in the prevalence of triple-resistant P. falciparum parasites. However, these parasites still circulate in the population and show clear resistance to piperaquine, mefloquine, and their combination. This study highlights the ability of P. falciparum to adapt to complex drug associations, which should be taken into consideration in future treatment strategies.