Department of Medical Microbiology and Clinical Microbiology, Near East University Faculty of Medicine, Near East Boulevard, 99138, Nicosia, Northern Cyprus.
Department of Medical Biology, Higher Institute of Medical Technology, Bandundu, Democratic Republic of the Congo.
Malar J. 2018 Jan 9;17(1):17. doi: 10.1186/s12936-017-2160-x.
Point mutations in Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthase (Pfdhps) genes which confer resistance to sulfadoxine-pyrimethamine (SP) occur at increasing rates. The present study aimed to identify Pfdhfr and Pfdhps mutations in P. falciparum isolates recovered from women who received two doses of SP during pregnancy in Bandundu, the Democratic Republic of Congo (DRC).
A total of 48 women with confirmed P. falciparum infection were enrolled in the study. Finger-prick blood samples that were collected on filter paper at the time of delivery were used for DNA isolation. Pfdhfr and Pfdhps genes were amplified by a nested PCR protocol. DNA sequencing was performed on both strands, and the point mutations were analysed.
All of the 48 (100.0%) P. falciparum isolates carried at least one polymorphism in both genes. The wild-type haplotypes of Pfdhfr (CNCSI [C50, N51, C59, S108, I164]) and Pfdhps (SAKAA [S436, A437, K540, A581, A613]) were not observed in the study. In Pfdhfr, N51I (85.4%), C59R (60.4%), and S108N (100.0%) polymorphisms were detected. Triple mutation (CIRNI) (mutant amino acids are underlined) was the most prevalent (47.9%) Pfdhfr haplotype. In the study, all P. falciparum isolates (100.0%) harboured the A437G allele in Pfdhps gene. Also, K540E and A581G polymorphisms were observed in one (2.1%) isolate. Single mutant haplotype (SGKAA) was detected in 97.9% of the isolates. Mutant Pfdhfr and Pfdhps allele combinations revealed quintuple (CICNI-SGEGA; 2.1%), quadruple (CIRNI-SGKAA; 47.9%), triple (CICNI-SGKAA; 35.4%, CNRNI-SGKAA; 12.5%), and double (CNCNI-SGKAA; 2.1%) haplotypes.
In the study, the rate of SGEGA haplotype was low (2.1%). Although K540E and A581G alleles are more common in Eastern Africa, a distinct lineage of SGEGA is also present in the DRC, which is located in Central Africa. This haplotype is associated with decreased efficacy of SP in pregnant women and infants, therefore, it should be carefully considered in the DRC and SP resistance should be routinely monitored.
疟原虫二氢叶酸还原酶（Pfdhfr）和二氢蝶酸合成酶（Pfdhps）基因中的点突变可导致对磺胺多辛-乙胺嘧啶（SP）的耐药性，其发生耐药性的比率正在不断增加。本研究旨在鉴定在刚果民主共和国（DRC）班顿杜接受两次孕期 SP 治疗的妇女中分离出的疟原虫 P. falciparum 中的 Pfdhfr 和 Pfdhps 突变。
共纳入 48 例经确认感染疟原虫 P. falciparum 的女性。分娩时采集手指末梢血样并置于滤纸上，用于 DNA 分离。通过巢式 PCR 方案扩增 Pfdhfr 和 Pfdhps 基因。对双链进行 DNA 测序，并分析点突变。
所有 48 例（100.0%）P. falciparum 分离株在这两个基因中均至少携带一种多态性。Pfdhfr（CNCSI [C50、N51、C59、S108、I164]）和 Pfdhps（SAKAA [S436、A437、K540、A581、A613]）的野生型单倍型在研究中未观察到。在 Pfdhfr 中，检测到 N51I（85.4%）、C59R（60.4%）和 S108N（100.0%）的多态性。最常见的 Pfdhfr 单倍型是三联突变（CIRNI）（突变氨基酸加下划线）（47.9%）。在本研究中，所有 P. falciparum 分离株（100.0%）均携带 Pfdhps 基因中的 A437G 等位基因。还观察到一个（2.1%）分离株存在 K540E 和 A581G 多态性。97.9%的分离株检测到单突变单倍型（SGKAA）。突变 Pfdhfr 和 Pfdhps 等位基因组合显示出五重（CICNI-SGEGA；2.1%）、四重（CIRNI-SGKAA；47.9%）、三重（CICNI-SGKAA；35.4%，CNRNI-SGKAA；12.5%）和双重（CNCNI-SGKAA；2.1%）单倍型。
在本研究中，SGEGA 单倍型的发生率较低（2.1%）。虽然 K540E 和 A581G 等位基因在东非更为常见，但在位于中非的 DRC 也存在独特的 SGEGA 谱系。这种单倍型与 SP 对孕妇和婴儿疗效降低有关，因此在 DRC 应谨慎考虑，应常规监测 SP 耐药性。
