Abstract
BackgroundThe Democratic Republic of Congo (DRC) malaria treatment policy recommends two first-line artemisinin-based combination therapies (ACTs) for the treatment of uncomplicated malaria: Artesunate-amodiaquine (ASAQ) and Artemether-lumefantrine (AL). This study investigated resistance to the ACTs currently in use in DRC through molecular markers in pfk13, pfcrt and pfmdr1 genes in Plasmodium falciparum isolated from patients returning for malaria retreatment. MethodsFrom November 2018 to November 2019, dried blood spots were taken from patients returning to health structures for fever within 28 days after an initial malaria treatment in 6 sentinel sites of National Malaria Control Programme (NMCP) across DRC. The new episode of malaria was first detected by a rapid diagnostic test (RDT) and then confirmed by a real-time PCR assay. Fragments of interest in pfk13 and pfcrt genes were amplified by conventional PCR before sequencing and Pfmdr1 gene copy number was determined by a TaqMan real-time PCR assay. ResultsOut of 474 enrolled patients, 364 (76.8%) were confirmed positive by PCR for P. falciparum. Of the 325 P. falciparum isolates successfully sequenced in pfk13-propeller gene, 7 (2.2%) carried non-synonymous (NS) mutations among which 3 previously reported (N498I, N554K and A557S) and 4 not yet reported (F506L, E507V, D516E and G538S). Of the 335 isolates successfully sequenced in pfcrt gene, 139 (41.5%) harbored the K76T mutation known to be associated with CQ resistance. The SVMNT haplotype associated with resistance to AQ has not been found. None of the isolates carried increased copy number of pfmdr1 gene among the 322 P. falciparum isolates successfully analyzed.ConclusionNo molecular marker known to date as associated with resistance to first-line ACTs in use was detected in P. falciparum isolated in patients returning for retreatment. Regular monitoring through in vivo drug efficacy and molecular studies must continue to ensure the effectiveness of the treatment of malaria in DRC.