Pang Yu, Zhu Damian, Zheng Huiwen, Shen Jing, Hu Yan, Liu Jie, Zhao Yanlin
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, China.
Clinical Laboratory, Chongqing Tuberculosis Control Institute, No. 71, Longteng Street, Jiulongpo District, Chongqing, 400050, People's Republic of China.
BMC Infect Dis. 2017 Nov 6;17(1):711. doi: 10.1186/s12879-017-2761-6.
Pyrazinamide (PZA) plays a unique role in the treatment for multidrug-resistant tuberculosis (MDR-TB) in both first- and second-line regimens. The aim of this study was to investigate the prevalence and molecular characterization of PZA resistance among MDR-TB isolates collected in Chongqing municipality.
A total of 133 MDR-TB isolates were collected from the smear-positive tuberculosis patients who were registered at local TB dispensaries of Chongqing. PZA susceptibility testing was determined with a Bactec MGIT 960 system. In addition, the genes conferring for PZA resistance were screened by DNA sequencing.
Of these 133 MDR-TB isolates, 83 (62.4%) were determined as PZA-resistant by MGIT 960. In addition, streptomycin- (83.1% vs. 56.0%, P < 0.01), ofloxacin- (51.8% vs. 18.0%, P < 0.01), kanamycin- (22.9% vs. 2.0%, P < 0.01), amikacin- (18.1% vs. 2.0%, P = 0.01), capromycin-resistance (12.0% vs. 2.0%, P = 0.05), were more frequently observed among PZA-resistant isolates compared with PZA-susceptible isolates. Sequence analysis revealed that 73 out of 83 (88.0%) MDR strains harbored a mutation located in the pncA gene, including 55 (75.3%, 55/73) of single nucleotide substitutions and 18 (24.7%, 18/73) of frameshift mutation, while no genetic mutation associated with PZA resistance was found in the rpsA gene. The pncA expression of strains harboring substitution from A to G at position -11 in the promoter region of pncA was significantly lower than that of H37Rv (P < 0.01).
In conclusion, our data have demonstrated that the analysis of the pncA gene rather than rpsA gene provides rapid and accurate information regarding PZA susceptibility for MDR-TB isolates in Chongqing. In addition, loss of pncA expression caused by promoter mutation confers PZA resistance in MDR-TB isolates.
吡嗪酰胺（PZA）在耐多药结核病（MDR-TB）一线和二线治疗方案中发挥着独特作用。本研究旨在调查重庆市收集的耐多药结核分枝杆菌分离株中PZA耐药情况及其分子特征。
从重庆市当地结核病防治所登记的涂片阳性肺结核患者中收集了133株耐多药结核分枝杆菌分离株。采用Bactec MGIT 960系统进行PZA药敏试验。此外，通过DNA测序筛选赋予PZA耐药性的基因。
在这133株耐多药结核分枝杆菌分离株中，83株（62.4%）经MGIT 960检测确定为对PZA耐药。此外，与PZA敏感株相比，PZA耐药株中链霉素耐药（83.1%对56.0%，P<0.01）、氧氟沙星耐药（51.8%对18.0%，P<0.01）、卡那霉素耐药（22.9%对2.0%，P<0.01）、阿米卡星耐药（18.1%对2.0%，P=0.01）、卷曲霉素耐药（12.0%对2.0%，P=0.05）的比例更高。序列分析显示，83株耐多药菌株中有73株（88.0%）在pncA基因发生突变，其中55株（75.3%，55/73）为单核苷酸替换，18株（24.7%，18/73）为移码突变，而在rpsA基因中未发现与PZA耐药相关的基因突变。pncA启动子区-11位由A替换为G的菌株，其pncA表达显著低于H37Rv（P<0.01）。
总之，我们的数据表明，对pncA基因而非rpsA基因进行分析可为重庆地区耐多药结核分枝杆菌分离株的PZA药敏情况提供快速准确的信息。此外，启动子突变导致的pncA表达缺失赋予了耐多药结核分枝杆菌分离株PZA耐药性。
