Prevalence of molecular markers associated with artemisinin, lumefantrine and amodiaquine resistance in pre-treatment isolates from two therapeutic efficacy monitoring sites in Guinea, 2016

Abstract

In Guinea, artemisinin-based combination therapy is the first-line antimalarial treatment for uncomplicated Plasmodium falciparum infection. There are limited data on the prevalence in Guinea of polymorphisms in the pfk13 gene (artemisinin resistance) and the pfmdr1 gene (amodiaquine 533 astmh.org and lumefantrine resistance). Since 2015, the National Malaria Control Program has implemented yearly therapeutic efficacy studies rotating between four sentinel sites in the country. We isolated DNA from 444 samples from study participants, including 421 pretreatments and 22 day-of-late treatment failure samples collected as part of the 2016 round of therapeutic efficacy studies in Mafèrinyah and Labé Health Districts. The pfk13 and pfmdr1 gene were amplified, sequenced and analyzed for polymorphisms. Of the 397 samples successfully analyzed, the majority of pretreatment (99%, 369/374) and all day-of-late treatment failure (100%, 22/22) samples were wild type for pfk13. Five pretreatment samples (1%, 5/374) carried synonymous mutations in the Kelch-propeller domain, including three in the artemether-lumefantrine arm (L429L, E509E and V510V) and two in the artesunate-amodiaquine arm (C469C and G496G). All five patients with pfk13 mutations were slide-negative on Day 3 and finished 28-day follow-up with adequate clinical and parasitological response. The NFD haplotype was the predominant pfmdr1 haplotype, present in 48% (189/391) of pretreatment samples, followed by the NYD haplotype, present in 33% (128/391) of pretreatment samples. Efficacy studies in 2016 in Mafèrinyah and Labé Health Districts showed genetic evidence of susceptibility to artemisinins, consistent with clinical outcome data showing 100% Day 3 clearance rates. Despite the absence of nonsynonymous pfk13 mutations, a substantial proportion of pretreatment isolates had pfmdr1 haplotypes previously associated with decreased lumefantrine susceptibility. Continued molecular monitoring is required at country level to ensure timely detection of antimalarial drug resistance and resistance-associated mutations.