Abanda Ngu Njei, Djieugoué Josiane Yvonne, Lim Eunjung, Pefura-Yone Eric Walter, Mbacham Wilfred Fon, Vernet Guy, Penlap Veronique Mbeng, Eyangoh Sara Irene, Taylor Diane Wallace, Leke Rose Gana Fomban
Biotechnology Centre, University of Yaounde I, PO Box: 3851, Yaounde, Cameroon.
Department of Tropical Medicine, Medical Microbiology and Pharmacology, University of Hawaii, Honolulu, HI, 96813, USA.
BMC Infect Dis. 2017 May 31;17(1):379. doi: 10.1186/s12879-017-2489-3.
Drug-resistant tuberculosis, especially multidrug-resistant tuberculosis (MDR-TB), is a major public health problem. Effective management of MDR-TB relies on accurate and rapid diagnosis. In this study, we assessed the diagnostic accuracy of the Genotype MTBDRplus assay in diagnosing MDR-TB in Cameroon, and then discuss on its utility within the diagnostic algorithm for MDR-TB.
In this cross-sectional study, 225 isolates of Mycobacterium tuberculosis cultured from sputum samples collected from new and previously treated pulmonary tuberculosis patients in Cameroon were used to determine the accuracy of the Genotype MTBDRplus assay. We compared the results of the Genotype MTBDRplus assay with those from the automated liquid culture BACTEC MGIT 960 SIRE system for sensitivity, specificity, and degree of agreement. The pattern of mutations associated with resistance to RIF and INH were also analyzed.
The Genotype MTBDRplus assay correctly identified Rifampicin (RIF) resistance in 48/49 isolates (sensitivity, 98% [CI, 89%-100%]), Isoniazid (INH) resistance in 55/60 isolates (sensitivity 92% [CI, 82%-96%]), and MDR-TB in 46/49 (sensitivity, 94% [CI, 83%-98%]). The specificity for the detection of RIF-resistant and MDR-TB cases was 100% (CI, 98%-100%), while that of INH resistance was 99% (CI, 97%-100%). The agreement between the two tests for the detection of MDR-TB was very good (Kappa = 0.96 [CI, 0.92-1.00]). Among the 3 missed MDR-TB cases, the Genotype MTBDRplus assay classified two samples as RIF-monoresistant and one as INH monoresistant. The most frequent mutations detected by the Genotype MTBDRplus assay was the rpoB S531 L MUT3 41/49 (84%) in RIF-resistant isolates, and the KatG S315 T1 (MUT1) 35/55 (64%) and inhA C15T (MUT1) 20/55 (36%) mutations in INH-resistant isolates.
The Genotype MTBDRplus assay had good accuracy and could be used for the diagnosis of MDR-TB in Cameroon. For routine MDR-TB diagnosis, this assay could be used for Mycobacterium tuberculosis cultures containing contaminants, to complement culture-based drug susceptibility testing or to determine drug resistant mutations.
耐药结核病，尤其是耐多药结核病（MDR-TB），是一个重大的公共卫生问题。耐多药结核病的有效管理依赖于准确快速的诊断。在本研究中，我们评估了Genotype MTBDRplus检测法在喀麦隆诊断耐多药结核病中的诊断准确性，然后讨论其在耐多药结核病诊断算法中的效用。
在这项横断面研究中，从喀麦隆新诊断和既往治疗过的肺结核患者痰液样本中培养出的225株结核分枝杆菌分离株用于确定Genotype MTBDRplus检测法的准确性。我们将Genotype MTBDRplus检测法的结果与自动液体培养BACTEC MGIT 960 SIRE系统的结果进行比较，以评估敏感性、特异性和一致性程度。还分析了与利福平（RIF）和异烟肼（INH）耐药相关的突变模式。
Genotype MTBDRplus检测法正确鉴定出48/49株分离株对利福平（RIF）耐药（敏感性98% [CI，89%-100%]），55/60株分离株对异烟肼（INH）耐药（敏感性92% [CI，82%-96%]），46/49株分离株为耐多药结核病（敏感性94% [CI，83%-98%]）。检测RIF耐药和耐多药结核病病例的特异性为100%（CI，98%-100%），而检测INH耐药的特异性为99%（CI，97%-100%）。两种检测方法在检测耐多药结核病方面的一致性非常好（Kappa = 0.96 [CI，0.92-1.00]）。在3例漏检的耐多药结核病病例中，Genotype MTBDRplus检测法将两个样本分类为仅对RIF耐药，一个样本分类为仅对INH耐药。Genotype MTBDRplus检测法检测到的最常见突变是耐RIF分离株中的rpoB S531L MUT3 41/49（84%），以及耐INH分离株中的KatG S315T1（MUT1）35/55（64%）和inhA C15T（MUT1）20/55（36%）突变。
Genotype MTBDRplus检测法具有良好的准确性，可用于喀麦隆耐多药结核病的诊断。对于常规耐多药结核病诊断，该检测法可用于含有污染物的结核分枝杆菌培养物，以补充基于培养的药敏试验或确定耐药突变。
