中国南方左氧氟沙星和莫西沙星耐药临床分离株的表型与基因型特征
Phenotypic and genotypic characterization of levofloxacin- and moxifloxacin-resistant clinical isolates in southern China.
作者信息
Hameed H M Adnan, Tan Yaoju, Islam Md Mahmudul, Guo Lingmin, Chhotaray Chiranjibi, Wang Shuai, Liu Zhiyong, Gao Yamin, Tan Shouyong, Yew Wing Wai, Zhong Nanshan, Liu Jianxiong, Zhang Tianyu
机构信息
State Key Laboratory of Respiratory Disease, Guangzhou Institutes of Biomedicine and Health (GIBH), Chinese Academy of Sciences (CAS), Guangzhou 510530, China.
University of Chinese Academy of Sciences (UCAS), Beijing 100049, China.
出版信息
J Thorac Dis. 2019 Nov;11(11):4613-4625. doi: 10.21037/jtd.2019.11.03.
BACKGROUND
Levofloxacin (LVX) and Moxifloxacin (MXF) are the cornerstones for treatment of multidrug-resistant tuberculosis (MDR-TB). China is one of the highest MDR- and fluoroquinolones (FQ)-resistant TB burdens countries. DNA gyrase encoded by genes is the main target of FQ in (MTB). The prevalence and molecular characterization of LVX- and MXF-resistant MTB strains from southern China were examined in this study.
METHODS
Drug susceptibility testing (DST) of 400 MTB clinical isolates was evaluated by proportion method on Löwenstein-Jensen (LJ) medium against ten drugs. The sequencing of entire and genes and multiplex PCR were performed to distinguish the prevalence of mutant types in Beijing and non-Beijing genotypes.
RESULTS
Three hundred and twenty-one out of four hundred (80.25%) drug-resistant isolates (resistant > one drug) were categorized as 83/321 (25.80%) MDR, 174/321 (54.20%) pre-XDR and 64/321 (19.93%) XDR-MTB. Overall, 303/400 (75.75%) LVX- and 292/400 (73.00%) MXF-resistant (R) MTB strains were identified. Two hundred seventy-one out of three hundred and three (89.43%) resistant strains carried mutations in and 91/303 (30.03%) in . Interestingly, 18 novel mutations were detected in and genes. Mutations at (A90, D94) and (T500, G510, G512) frequently existed in QRDR(s) of and respectively in 286/400 (71.50%) LVXMXF strains. The novel mutations in- and out-side the QRDR of (L105R, A126E, M127K, D151T, V165A) and (D461H, N499S, G520A) increased the sensitivity and consistency of genotypic tests. Notably, 25 LVXMXF strains were found with unknown resistance mechanisms.
CONCLUSIONS
Mutations in QRDR(s) were concomitantly associated with Beijing and non-Beijing genotypes. The prevalence of resistance and cross-resistance between LVX and MXF in MTB isolates from southern China was immensely higher than other countries. Our valuable findings provide the substantial implications to improve the reliability of genotypic diagnostic tests relying on potential resistance conferring mutations in entire genes.
背景
左氧氟沙星（LVX）和莫西沙星（MXF）是治疗耐多药结核病（MDR-TB）的基石。中国是耐多药和耐氟喹诺酮类（FQ）结核病负担最高的国家之一。由gyrA和gyrB基因编码的DNA促旋酶是结核分枝杆菌（MTB）中FQ的主要靶点。本研究检测了中国南方耐LVX和耐MXF的MTB菌株的流行情况及分子特征。
方法
采用比例法在改良罗氏（LJ）培养基上对400株MTB临床分离株进行针对10种药物的药敏试验（DST）。对gyrA和gyrB基因全长进行测序并进行多重PCR，以区分北京和非北京基因型中突变类型的流行情况。
结果
400株耐药分离株（对一种以上药物耐药）中有321株（80.25%）被分类为83/321（25.80%）MDR、174/321（54.20%）pre-XDR和64/321（19.93%）XDR-MTB。总体而言，鉴定出303/400（75.75%）耐LVX和292/400（73.00%）耐MXF（R）的MTB菌株。303株耐药菌株中有271株（89.43%）在gyrA基因发生突变，91/30（30.03%）在gyrB基因发生突变。有趣的是，在gyrA和gyrB基因中检测到18个新突变。gyrA和gyrB基因喹诺酮耐药决定区（QRDR）的（A90、D94）和（T500、G510、G512）突变分别在286/400（71.50%）的LVX-MXF菌株中频繁存在。gyrA基因QRDR内外的新突变（L105R、A126E、M127K、D151T、V165A）和gyrB基因（D461H、N499S、G520A）提高了基因分型检测的敏感性和一致性。值得注意的是，发现25株LVX-MXF菌株耐药机制不明。
结论
QRDR中的突变与北京和非北京基因型同时相关。中国南方MTB分离株中LVX和MXF之间的耐药及交叉耐药流行率远高于其他国家。我们的重要发现为提高基于gyrA和gyrB基因潜在耐药突变的基因诊断检测的可靠性提供了重要意义。
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