TB and HIV Directorate, Ethiopian Public Health Institute, Addis Ababa, Ethiopia.
Department of Microbial, Cellular and Molecular Biology, Addis Ababa University, Addis Ababa, Ethiopia.
PLoS One. 2022 Sep 13;17(9):e0274426. doi: 10.1371/journal.pone.0274426. eCollection 2022.
Traditionally, single critical concentrations of drugs are utilized for Mycobacterium tuberculosis (Mtb) drug susceptibility testing (DST); however, the level of drug resistance can impact treatment choices and outcomes. Mutations at the katG gene are the major genetic mutations in multidrug resistant (MDR) Mtb and usually associated with high level resistance. We assessed the minimum inhibitory concentrations (MICs) of MDR or rifampin resistant (RR) and isoniazid (INH) resistant Mtb isolates to determine the quantification of drug resistance among key anti-tuberculosis drugs.
The study was conducted on stored Mtb isolates collected as part of a national drug resistance survey in Ethiopia. MIC values were determined using Sensititre™ MYCOTB plates. A line probe assay (MTBDRplus) was also performed to identify genetic determinants of resistance for all isolates.
MIC testing was performed on 74 Mtb isolates including 46 MDR, 2 RR and 26 INH phenotypically resistant isolates as determined by the Löwenstein Jensen (LJ) method. Four (15%) INH resistant Mtb isolates were detected as borderline rifampin resistance (MIC = 1 μg/ml) using MYCOTB MIC plates and no rifampin resistance mutations were detected by LPA. Among the 48 MDR/RR TB cases, 9 (19%) were rifabutin susceptible (MIC was between ≤0.25 and 0.5μg/ml). Additionally, the MIC for isoniazid was between 2-4 μg/ml (moderate resistance) for 58% of MDR TB isolates and 95.6% (n = 25) of the isolates had mutations at the katG gene.
Our findings suggest a role for rifabutin treatment in a subset of RR TB patients, thus potentially preserving an important drug class. The high proportion of moderate level INH resistant among MDR Mtb isolates indicates the potential benefit of high dose isoniazid treatment in a high proportion of katG gene harboring MDR Mtb isolates.
传统上，单一临界药物浓度用于结核分枝杆菌（Mtb）药物敏感性测试（DST）；然而，耐药水平会影响治疗选择和结果。katG 基因突变是耐多药（MDR）结核分枝杆菌的主要遗传突变，通常与高水平耐药相关。我们评估了耐多药或利福平耐药（RR）和异烟肼（INH）耐药 Mtb 分离物的最低抑菌浓度（MIC），以确定关键抗结核药物的耐药定量。
本研究在埃塞俄比亚全国耐药性调查中收集的储存 Mtb 分离物上进行。使用 Sensititre™ MYCOTB 平板测定 MIC 值。还对所有分离物进行线探针分析（MTBDRplus）以鉴定耐药的遗传决定因素。
对 74 株 Mtb 分离物进行了 MIC 检测，包括 46 株 MDR、2 株 RR 和 26 株 INH 表型耐药分离物，如 Löwenstein Jensen（LJ）方法确定的那样。4 株（15%）INH 耐药 Mtb 分离物用 MYCOTB MIC 平板检测到边界利福平耐药（MIC=1μg/ml），LPA 未检测到利福平耐药突变。在 48 例 MDR/RR 结核病病例中，9 例（19%）利福布汀敏感（MIC 在 0.25-0.5μg/ml 之间）。此外，58%的 MDR 结核病分离物的异烟肼 MIC 为 2-4μg/ml（中度耐药），95.6%（n=25）的分离物 katG 基因有突变。
我们的研究结果表明，利福布丁治疗 RR 结核病患者的一部分可能发挥作用，从而潜在地保留了一种重要的药物类别。MDR Mtb 分离物中中等水平 INH 耐药的比例很高，表明高剂量异烟肼治疗在携带 katG 基因的 MDR Mtb 分离物中比例很高的情况下具有潜在的益处。
