Convenient screening for drug resistance mutations from historical febrile malaria samples across Kenya

BackgroundHistorically, chloroquine resistance emerged that was driven by mutations in the chloroquine resistance transporter (Pfcrt) gene. This led to the global withdrawal of chloroquine in 1998 and its subsequent replacement with sulfadoxine-pyrimethamine, whose efficacy was compromised by a high prevalence of mutations in the dihydrofolate reductase and the dihydropteroate synthase genes by 2004. Consequently, artemisinin-based combination therapies (ACTs) were introduced in 2006. Since then, thirteen mutations in the kelch 13 (Pfk13) propeller domain have emerged and validated by the World Health Organization (WHO) as markers of partial artemisinin resistance. This study aimed to characterize temporal trends in both established, Pfcrt and Pfk13 and less well-described potential markers, cysteine desulfurase (Pfnfs) and Pfcoronin, using febrile malaria samples collected across diverse regions of Kenya between 2013 and 2022. MethodsThe temporal trend of these markers of resistance were assessed by screening archived P. falciparum positive dried blood spots (DBS). A total of 1,750 DBS samples collected from Therapeutic Efficacy Studies (TES) conducted in: Kwale (2013, n=350), Kisumu (2015, n=314), Busia (2016, n=334), Kisii (2017, n=314), Kwale (2018, n=150), and a hrp2 study conducted Kisii (2022, n=288). Parasite genomic DNA was extracted using the Chelex-saponin method and confirmed by a Pf 18S RT-PCR. Pfk13, Pfcrt, Pfnfs and Pfcoronin PCR amplicons were sequenced using capillary electrophoresis, Illumina Miseq or the Oxford Nanopore (GridION) platform. ResultsThe prevalence of Pfcrt mutations declined over time and no WHO validated Pfk13 mutations associated with artemisinin resistance were detected. However, synonymous substitutions at WHO-validated codons C469C and P553P were identified. In the PfCoronin gene, non-synonymous mutations distinct from those reported in West Africa were observed at high frequencies (>75%). Notably, the Pfnfs-K65Q mutation, previously associated with reduced lumefantrine sensitivity in West Africa, was detected in over 80% of samples. Our findings reveal differences in some antimalarial resistance genetic markers between observations made in The Gambia and Senegal (West Africa) and Kilifi (East Africa). Based on the convenient sample set, there were no WHO validated k13 mutations up until 2022, suggesting continued ACT efficacy in Kenya. This study underscores the importance of continued molecular surveillance and suggests that resistance may evolve through different pathways in East compared to West Africa and Southeast Asia.