Kanji Akbar, Hasan Rumina, Zhang Ying, Shi Wanliang, Imtiaz Kehkashan, Iqbal Kiran, Shafiq Samreen, Hasan Zahra
Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan.
Int J Mycobacteriol. 2016 Dec;5 Suppl 1:S150. doi: 10.1016/j.ijmyco.2016.09.067. Epub 2016 Nov 25.
Extensively drug-resistant tuberculosis (XDR-TB) is defined as tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) strains that are multidrug resistant (MDR) and also resistant to a fluoroquinolone and to one injectable aminoglycoside or capreomycin. Whilst resistance in MTB has been associated with single nucleotide polymorphisms (SNPs), efflux pumps are thought to play a role in conferring resistance to MTB but little is known about them.
We studied XDR MTB (n=10) strains characterized by whole genome sequencing (WGS; http://www.ebi.ac.uk/ena/data/view/PRJEB7798). Phenotypic susceptibility testing was performed by the MGIT 960 (Becton, Dickinson and Co., NJ, USA) method. All XDR MTB strains were resistant to at least seven drugs whilst one XDR MTB strain, X54 was resistant to isoniazid, rifampicin, pyrazinamide, streptomycin, ethambutol, fluoroquinolones, capreomycin, kanamycin, amikacin, and ethionamide. The mRNA expression of efflux candidate genes Rv0194, Rv2688c, Rv1634, drrA, and drrB was determined in XDR MTB strains as compared with the ATCC reference strain, H37Rv, and drug-susceptible (DS) MTB (n=9) strains using the relative quantification method normalized to 16S rRNA.
The mRNA expression levels of efflux genes Rv2688c (p=0.0037), Rv1634 (p=0.0042), drrA (p=0.0078) and drrB (p=0.0003) were upregulated in XDR-TB strains as compared with DS MTB strains.
The differences between XDR-TB and drug-susceptible isolates suggest that the increased expression levels of MTB efflux pump genes may contribute to drug resistance in extensively drug-resistant tuberculosis. Future studies are needed to determine whether combining efflux pump inhibitors to antitubercular drugs would be effective to treat resistant tuberculosis.
广泛耐药结核病（XDR-TB）被定义为由结核分枝杆菌（MTB）菌株引起的结核病，这些菌株对多种药物耐药（MDR），并且对一种氟喹诺酮类药物以及一种注射用氨基糖苷类药物或卷曲霉素耐药。虽然MTB中的耐药性与单核苷酸多态性（SNP）有关，但外排泵被认为在赋予MTB耐药性方面起作用，但对此了解甚少。
我们研究了通过全基因组测序（WGS；http://www.ebi.ac.uk/ena/data/view/PRJEB7798）鉴定的XDR MTB（n = 10）菌株。采用MGIT 960（美国新泽西州BD公司）方法进行表型药敏试验。所有XDR MTB菌株对至少七种药物耐药，而一株XDR MTB菌株X54对异烟肼、利福平、吡嗪酰胺、链霉素、乙胺丁醇、氟喹诺酮类、卷曲霉素、卡那霉素、阿米卡星和乙硫异烟胺耐药。与ATCC参考菌株H37Rv和药物敏感（DS）MTB（n = 9）菌株相比，使用归一化至16S rRNA的相对定量方法测定XDR MTB菌株中外排候选基因Rv0194、Rv2688c、Rv1634、drrA和drrB的mRNA表达。
与DS MTB菌株相比，XDR-TB菌株中外排基因Rv2688c（p = 0.0037）、Rv1634（p = 0.0042）、drrA（p = 0.0078）和drrB（p = 0.0003）的mRNA表达水平上调。
XDR-TB与药物敏感菌株之间的差异表明，MTB外排泵基因表达水平的增加可能导致广泛耐药结核病的耐药性。需要进一步研究以确定将外排泵抑制剂与抗结核药物联合使用是否能有效治疗耐药结核病。
