Centre for International Health, Faculty of Medicine, University of Bergen, Bergen, Norway; University of Zambia, School of Health Sciences, Department of Biomedical Sciences, Lusaka, Zambia; School of Medicine and University Teaching Hospital Malaria Research Unit, University of Zambia, Lusaka, Zambia.
PATH Malaria Control and Elimination Partnership in Africa, National Malaria Elimination Centre, Ministry of Health, Lusaka, Zambia.
Acta Trop. 2020 Dec;212:105704. doi: 10.1016/j.actatropica.2020.105704. Epub 2020 Sep 29.
Antimalarial resistance is an inevitable feature of control efforts and a key threat to achieving malaria elimination. Plasmodium falciparum, the deadliest of several species causing human malaria, has developed resistance to essentially all antimalarials. This study sought to investigate the prevalence of molecular markers associated with resistance to sulfadoxine-pyrimethamine (SP) and artemether-lumefantrine (AL) in Southern and Western provinces in Zambia. SP is used primarily for intermittent preventive treatment during pregnancy, while AL is the first-line antimalarial for uncomplicated malaria in Zambia. Blood samples were collected from household members of all ages in a cross-sectional survey conducted during peak malaria transmission, April to May of 2017, and amplified by polymerase chain reaction (PCR). Amplicons were then analysed by high-resolution melt following PCR to identify mutations associated with SP resistance in the P. falciparum dihydrofolate reductase (Pfdhfr) and P. falciparum dihydropteroate synthase (Pfdhps) genes and lumefantrine resistance in the P. falciparum multi-drug resistance 1 (Pfmdr1) gene. Finally, artemether resistance was assessed in the P. falciparum Kelch 13 (PfK13) gene using nested PCR followed by amplicon sequencing. The results showed a high frequency of genotypic-resistant Pfdhps A437G (93.2%) and Pfdhfr C59R (86.7%), N51I (80.9%), and S108N (80.8%) of which a high proportion (82.4%) were quadruple mutants (Pfdhfr N51I, C59R, S108N +Pfdhps A437G). Pfmrd1 N86Y, Y186F, and D1246Y - NFD mutant haplotypes were observed in 41.9% of isolates. The high prevalence of quadruple dhps/dhfr mutants indicates strong antifolate drug pressure from SP or other drugs (e.g., co-trimoxazole). Three samples contained PfK13 mutations, two synonymous (T478 and V666) and one non-synonymous (A578S), none of which have been associated with delayed clearance. This suggests that artemisinin remains efficacious in Zambia, however, the moderately high prevalence of approximately 40% Pfmdr1 NFD mutations calls for close monitoring of AL.
抗疟药物耐药性是控制工作中不可避免的特征，也是实现消除疟疾的关键威胁。恶性疟原虫是几种导致人类疟疾的最致命物种之一，已经对基本上所有的抗疟药物产生了耐药性。本研究旨在调查赞比亚南部和西部地区与磺胺多辛-乙胺嘧啶（SP）和青蒿琥酯-甲氟喹（AL）耐药相关的分子标记物的流行情况。SP 主要用于妊娠期间的间歇性预防治疗，而 AL 是赞比亚治疗无并发症疟疾的一线抗疟药物。在 2017 年 4 月至 5 月的疟疾传播高峰期，通过横断面调查采集了各个年龄段家庭成的血液样本，并通过聚合酶链反应（PCR）进行扩增。然后通过聚合酶链反应后高分辨率熔解（PCR-HRM）分析扩增子，以鉴定恶性疟原虫二氢叶酸还原酶（Pfdhfr）和恶性疟原虫二氢蝶酸合成酶（Pfdhps）基因中与 SP 耐药相关的突变，以及恶性疟原虫多药耐药 1（Pfmdr1）基因中与 lumefantrine 耐药相关的突变。最后，使用嵌套 PCR 后扩增子测序评估恶性疟原虫 Kelch 13（PfK13）基因中的 artemether 耐药性。结果显示，Pfdhps A437G（93.2%）和 Pfdhfr C59R（86.7%）、N51I（80.9%）和 S108N（80.8%）基因型耐药的高频发生，其中高比例（82.4%）为四重突变体（Pfdhfr N51I、C59R、S108N+Pfdhps A437G）。Pfmdr1 N86Y、Y186F 和 D1246Y-NFD 突变单倍型在 41.9%的分离株中观察到。高水平的四重 dhps/dhfr 突变体表明 SP 或其他药物（如复方新诺明）存在强烈的抗叶酸药物压力。有 3 个样本含有 PfK13 突变，其中 2 个同义突变（T478 和 V666）和 1 个非同义突变（A578S），均与清除延迟无关。这表明青蒿素在赞比亚仍然有效，然而，大约 40%的 Pfmdr1 NFD 突变的中度高流行率需要密切监测 AL。
