Chikaonda Tarsizio, Ketseoglou Irene, Nguluwe Nelson, Krysiak Robert, Thengolose Isaac, Nyakwawa Felix, Rosenberg Nora E, Stanley Christopher, Mpunga James, Hoffman Irving F, Papathanasopoulos Maria A, Hosseinipour Mina, Scott Lesley, Stevens Wendy
Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa.
UNC Project, Lilongwe, Malawi.
Afr J Lab Med. 2017 Mar 31;6(2):463. doi: 10.4102/ajlm.v6i2.463. eCollection 2017.
Availability and access to the detection of resistance to anti-tuberculosis drugs remains a significant challenge in Malawi due to limited diagnostic services. The Xpert MTB/RIF can detect and resistance to rifampicin in a single, rapid assay. Rifampicin-resistant has not been well studied in Malawi.
We aimed to determine mutations in the rifampicin resistance determining region (RRDR) of the B gene of strains which were defined as resistant to rifampicin by the Xpert MTB/RIF assay.
Rifampicin-resistant isolates from 43 adult patients (≥ 18 years) from various districts of Malawi were characterised for mutations in the RRDR (codons 507-533) of the B gene by DNA sequencing.
Mutations were found in 37/43 (86%) of the resistant isolates in codons 511, 512, 513, 516, 522, 526 and 531. The most common mutations were in codons 526 (38%), 531 (29.7%) and 516 (16.2%). Mutations were not found in 6/43 (14%) of the resistant isolates. No novel B mutations other than those previously described were found among the rifampicin-resistant complex strains.
This study is the first to characterise rifampicin resistance in Malawi. The chain-termination DNA sequencing employed in this study is a standard method for the determination of nucleotide sequences and can be used to confirm rifampicin resistance obtained using other assays, including the Xpert MTB/RIF. Further molecular cluster analysis, such as spoligotyping and DNA finger printing, is still required to determine transmission dynamics and the epidemiological link of the mutated strains.
由于诊断服务有限，在马拉维，抗结核药物耐药性检测的可及性和获取途径仍然是一项重大挑战。Xpert MTB/RIF检测能够在单一快速检测中同时检测结核分枝杆菌和利福平耐药性。在马拉维，对利福平耐药的结核分枝杆菌尚未得到充分研究。
我们旨在确定通过Xpert MTB/RIF检测法判定为利福平耐药的结核分枝杆菌菌株B基因利福平耐药决定区（RRDR）中的突变。
通过DNA测序，对来自马拉维不同地区的43名成年患者（≥18岁）的利福平耐药分离株进行B基因RRDR（第507 - 533密码子）突变特征分析。
在37/43（86%）的耐药分离株中，第511、512、513、516、522、526和531密码子发现了突变。最常见的突变发生在第526密码子（38%）、第531密码子（29.7%）和第516密码子（16.2%）。6/43（14%）的耐药分离株未发现突变。在利福平耐药的结核分枝杆菌复合菌株中，未发现除先前描述之外的新型B基因突变。
本研究首次对马拉维的利福平耐药情况进行了特征分析。本研究中采用的链终止DNA测序是测定核苷酸序列的标准方法，可用于确认使用其他检测方法（包括Xpert MTB/RIF）获得的利福平耐药性。仍需要进一步的分子聚类分析，如间隔寡核苷酸分型和DNA指纹图谱分析，以确定突变菌株的传播动态和流行病学联系。
