Shahi Fatemeh, Khosravi Azar Dokht, Tabandeh Mohammad Reza, Salmanzadeh Shokrollah
Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Heliyon. 2021 Jul 12;7(7):e07566. doi: 10.1016/j.heliyon.2021.e07566. eCollection 2021 Jul.
Different resistance mechanisms for multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have been reported. Although mutations in target genes are the main cause of drug resistance, efflux pumps (Eps) also play an important role in this process. Here, we investigated the overexpression of five putative EP genes plus gene mutations in MDR-TB clinical isolates.
A total of 27 (Mtb) clinical isolates including, 22 MDR and 5 sensitive isolates were analyzed. Minimum inhibitory concentrations (MIC) were determined in the absence and presence of efflux inhibitor. The expression level of 5 EP genes (, , , , ) was investigated by quantitative real time PCR (RT-qPCR). DNA sequencing of , , and promoter was done.
Among the 22 MDR-TB isolates, 13 (59.1%) showed significant overexpression (>4-fold) for at least one EP gene. The expression levels of 5 genes were significantly higher (P < 0.05) in MDR-TB isolates than sensitive isolates. The (22.7%), and (18.2%) were found to be the most commonly overexpressed EPs. The observed MICs were as follows: RIF (2 to >128 μg/ml) and INH (2-32 μg/ml). After efflux pump inhibitor exposure, 10/22 (45.45%) isolates showed a decrease in MIC of INH, and 17/22 (77.27%) isolates showed a decrease in MIC of RIF. Of the isolates that overexpressed, 4 isolates lacked mutation in , , and genes and 10 ones lacked mutation in and .
The results showed that overexpression of EP genes in Mtb isolates, besides target gene mutations can contribute to the development of MDR phenotype.
已有报道指出耐多药结核病（MDR-TB）和广泛耐药结核病（XDR-TB）存在不同的耐药机制。虽然靶基因突变是耐药的主要原因，但外排泵（Eps）在此过程中也起重要作用。在此，我们研究了5个假定的EP基因的过表达以及MDR-TB临床分离株中的基因突变情况。
共分析了27株结核分枝杆菌（Mtb）临床分离株，包括22株MDR分离株和5株敏感分离株。在有无外排抑制剂的情况下测定最低抑菌浓度（MIC）。通过定量实时PCR（RT-qPCR）研究5个EP基因（、、、、）的表达水平。对、和启动子进行DNA测序。
在22株MDR-TB分离株中，13株（59.1%）至少有一个EP基因显著过表达（>4倍）。MDR-TB分离株中5个基因的表达水平显著高于敏感分离株（P<0.05）。发现（22.7%）和（18.2%）是最常过表达的Eps。观察到的MIC如下：利福平（2至>128μg/ml）和异烟肼（2 - 32μg/ml）。在外排泵抑制剂作用后，10/22（45.45%）的分离株异烟肼MIC降低，17/22（77.27%）的分离株利福平MIC降低。在过表达的分离株中，4株、和基因无突变，10株和基因无突变。
结果表明，除了靶基因突变外，Mtb分离株中EP基因的过表达也可能导致MDR表型的产生。
