CHỈ ĐIỂM PHÂN TỬ KHÁNG THUỐC SỐT RÉT TRÊN CÁC PHÂN LẬP PLASMODIUM FALCIPARUM: MỘT NGHIÊN CỨU QUAN SÁT TẠI ĐĂK LĂK TỪ 2017-2020

Abstract

Backgrounds: Emerging artemisinin-based combination (ACTs) resistance in Vietnam poses a significant risk to malaria elimination roadmap by 2030. Since 2009, P. falciparum strains have shown decreased susceptibility to artemisinin and delayed asexual parasite clearance after ACTs treatment in Highland zone, except Dak Lak province. Understanding the genetic phenotype of ACTs resistance is crucial for early warning sign surveillance.

^{Methods: This study assessed molecular markers associated with resistance to} dihydroartemisinin-piperaquine, ^{artesunate-mefloquine via dried-blood spots (DBS) isolate samples collected from falciparum malaria patients enrolled in a multicenter observational study during 2017-2020. All isolateswere analysed for the drug resistance markers in the Pfk13 propeller domain, Pfplasmepsine2, Pfmdr1, and Pfcrt genes by Sanger sequencing. Additionally, the Pfpm2 gene copy number was assessed by real-time polymerase chain reaction. DNA was purifed with QIAamp DNA Mini kits (QIAGEN; Düsseldorf, Germany), all genotypes were generated by selective regions amplicon sequencing of the parasite genome at Wellcome Sanger Institute (UK), Pasteur Institute (Cambodia), First Base DNA sequencingAxil Scientific Pte.,(Singapore),  then genotypes were translated into drug resistance haplotypes.}

Findings: A total of 55 and 79 isolate samples of microscopically diagnosed P. falciparumisolates were collected from Dak Lak province in 2017-2018 and 2019-2020, respectively.The results indicate presence of both high proportion of Pfk13-C580Y mutations associated with artemisinin resistancefrom 83.6% (46/55) to 100% (79/79) and thePfPlasmepsine 2amplication (>1.5 copy) from 20% (11/55) to 77.2% (61/79) and exonuclease E415G mutation which is linked with piperaquine resistancefrom 88.5% (44/55) to 91.1% (72/79) as well in period 2017-2018 and 2019-2020, respectively. On the other hand, frequency of other 4-aminoquinoline resistance mutations in Pfcrt (72-76 CVIET) of 92.7% (51/55) and 91.1% (72/79), very few mutations were found in Pfcrt (72-76CVIDT), Pfcrt (72-76 CVVET), Pfcrt (72-76 WGIET), Pfcrt F145I markers (<5%). There was a noteworthy point of high proportion of mutations in Pfmdr1 (>1.5 copy)conferring mefloquine resistancefrom 23.6% (13/55) in years 2017-2018, but only 1.3% (1/79) in years 2019-2020. Noteworthy, high proportion of double Pfk13-C580Y mutations plus PfPlasmepsine 2amplication (resistance to DHA-PPQ) were 16.4% (9/55) and 77.2% (61/79), and Pfk13-C580Y mutations plus Pfmdr1CNV (resistance to ASMQ) were 21.8% (12/55) and 1.3% (1/79) in 2017-2018 and 2019-2020, respectively. There is no isolate with triple or quadruple mutations in this study.

Conclusion: The results showed presence high proportion of alone and double Pfk13-C580Ymutations and PfPlasmepsine 2 amplication/ exonuclease E415G mutationassociated with artemisinin and piperaquine resistance. High proportion of mutations in Pfmdr1 which is linked with mefloquine resistance need to be more strictly surveillance. Role of monitoring for molecular markers of ACT resistance is needed to complement clinical data to inform National treatment policy in Vietnam.