Huo Fengmin, Ma Yifeng, Li Shanshan, Xue Yi, Shang Yuanyuan, Dong Lingling, Li Yunxu, Pang Yu
National Clinical Laboratory on Tuberculosis, Beijing Key Laboratory on Drug-Resistant Tuberculosis Research, Beijing Chest Hospital, Capital Medical University, Beijing Tuberculosis and Thoracic Tumor Institute, Beijing, People's Republic of China.
National Clinical Laboratory on Tuberculosis, Beijing Key Laboratory on Drug-Resistant Tuberculosis Research, Beijing Chest Hospital, Capital Medical University, Beijing Tuberculosis and Thoracic Tumor Institute, Beijing, People's Republic of China.
J Mol Diagn. 2020 Sep;22(9):1199-1204. doi: 10.1016/j.jmoldx.2020.06.010. Epub 2020 Jun 30.
Although rapid, highly sensitive molecular diagnostics tests are useful for diagnosing fluoroquinolone-resistant tuberculosis (TB), results of molecular testing versus conventional sequential phenotypic drug susceptibility testing (pDST) are frequently discordant. This article determined the discordance rate of levofloxacin (LFX) resistance results, obtained via MeltPro TB molecular testing, versus pDST of clinical TB isolates collected in Beijing, China, between January and December 2018. Isolates with discordant results were further subjected to LFX minimal inhibitory concentration (MIC) determinations and DNA sequence analysis to explore causes of discordance. Of 571 total TB cases, 126 (22.1%) were identified as LFX resistant using the MeltPro TB assay. However, 34 of these 126 LFX-resistant isolates yielded LFX-susceptible test results using pDST, for an overall discordance rate of 27.0%. LFX MICs mainly clustered around the critical LFX concentration, with 7 (21.2%) and 13 (39.4%) of isolates exhibiting MICs of 2.0 and 4.0 mg/L, respectively. The most prevalent LFX resistance mutations associated with discordant results were involved in DNA gyrase subunit A amino acid substitutions Ala90Val (13, 39.4%) and Asp94Ala (11, 33.3%). Notably, more than one-quarter of isolates deemed LFX resistant via the MeltPro assay were scored as LFX susceptible on the basis of pDST results. Ultimately, highly discordant LFX-resistance test results were associated with specific gyrA mutations in isolates with MICs approaching the critical LFX concentration.
尽管快速、高灵敏度的分子诊断检测对于诊断耐氟喹诺酮类结核病（TB）很有用，但分子检测结果与传统的序贯表型药物敏感性检测（pDST）结果经常不一致。本文确定了2018年1月至12月在中国北京收集的临床结核分枝杆菌分离株通过MeltPro TB分子检测获得的左氧氟沙星（LFX）耐药结果与pDST结果之间的不一致率。对结果不一致的分离株进一步进行LFX最低抑菌浓度（MIC）测定和DNA序列分析，以探究不一致的原因。在571例结核病病例中，使用MeltPro TB检测法鉴定出126例（22.1%）为LFX耐药。然而，这126株LFX耐药分离株中有34株使用pDST检测结果为LFX敏感，总体不一致率为27.0%。LFX的MIC主要聚集在LFX临界浓度附近，分别有7株（21.2%）和13株（39.4%）分离株的MIC为2.0和4.0mg/L。与结果不一致相关的最常见LFX耐药突变涉及DNA旋转酶亚基A氨基酸取代Ala90Val（13株，39.4%）和Asp94Ala（11株，33.3%）。值得注意的是，超过四分之一通过MeltPro检测法判定为LFX耐药的分离株根据pDST结果被判定为LFX敏感。最终，LFX耐药检测结果高度不一致与MIC接近LFX临界浓度的分离株中的特定gyrA突变有关。
