Oh Tae Sang, Kim Young Jin, Kang Hee Yoon, Kim Chang-Ki, Cho Sun Young, Lee Hee Joo
Department of Laboratory Medicine, Kyung Hee University Hospital, Seoul, Republic of Korea.
Department of Laboratory Medicine, Kyung Hee University School of Medicine, Seoul, Republic of Korea.
Infect Genet Evol. 2017 Apr;49:111-115. doi: 10.1016/j.meegid.2017.01.002. Epub 2017 Jan 3.
Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis, is an important communicable disease. Various mechanisms of resistance to antituberculosis drugs have been reported; these are principally mutations in target genes. However, not all M. tuberculosis resistance can be explained by mutations in such genes. Other resistance mechanisms associated with drug transport, such as efflux pumps, have also been reported. In this study, we investigated the expression levels of three putative efflux pumps and mutations in target genes associated with injectable agents and fluoroquinolones with clinical MDR and XDR-TB isolates. Thirty clinical isolates of M. tuberculosis that had been phenotypically characterized were obtained from the Korean Institute of Tuberculosis. Of these, 14 were MDR-TB isolates resistant to at least one injectable aminoglycoside (amikacin; AMK, kanamycin; KAN, and/or capreomycin; CPM) and 16 were XDR-TB isolates. M. tuberculosis H37Rv (ATCC 27249) was used as a reference strain. Five putative genes (Rv1258c, Rv2686c, Rv2687c, Rv2688c and pstB) were selected for analysis in this study. Sequencing was performed to detect mutations in rrs and eis genes. qRT-PCR was performed to investigate expression levels of five efflux pump genes. Of the 30 isolates, 25 strains had mutations in rrs associated with resistance to KAN, CPM and AMK and two strains had eis mutations, as well as mutations in rrs. pstB (Rv0933) exhibited increased expression and Rv2687c and Rv2688c exhibited decreased expression compared to the reference strain. Increased expression of pstB in clinical drug-resistant tuberculosis isolates may contribute to drug resistance in M. tuberculosis. In our case, overexpression of Rv1258c may have been associated with resistance to kanamycin. No correlation was evident between Rv2686c, Rv2687c or Rv2688c expression and fluoroquinolone resistance. To explore the details of efflux pump drug-resistance mechanisms, further studies on efflux pump inhibitors, transcriptional regulators, such as whiB7, and additional efflux pump genes are needed.
由结核分枝杆菌感染引起的结核病是一种重要的传染病。已报道了多种对抗结核药物的耐药机制；这些主要是靶基因的突变。然而，并非所有结核分枝杆菌的耐药性都可以用此类基因的突变来解释。还报道了其他与药物转运相关的耐药机制，如外排泵。在本研究中，我们调查了三种假定外排泵的表达水平以及与注射剂和氟喹诺酮类药物相关的靶基因的突变情况，使用的是临床耐多药和广泛耐药结核分枝杆菌分离株。从韩国结核病研究所获得了30株已进行表型特征鉴定的结核分枝杆菌临床分离株。其中，14株是对至少一种注射用氨基糖苷类药物（阿米卡星；AMK、卡那霉素；KAN和/或卷曲霉素；CPM）耐药的耐多药结核分枝杆菌分离株，16株是广泛耐药结核分枝杆菌分离株。结核分枝杆菌H37Rv（ATCC 27249）用作参考菌株。本研究选择了五个假定基因（Rv1258c、Rv2686c、Rv2687c、Rv2688c和pstB）进行分析。进行测序以检测rrs和eis基因中的突变。进行qRT-PCR以研究五个外排泵基因的表达水平。在30株分离株中，25株菌株的rrs基因发生了与对KAN、CPM和AMK耐药相关的突变，两株菌株既有eis基因突变，也有rrs基因突变。与参考菌株相比，pstB（Rv0933）表达增加，Rv2687c和Rv2688c表达降低。临床耐多药结核分枝杆菌分离株中pstB表达增加可能导致结核分枝杆菌耐药。在我们的病例中，Rv1258c的过表达可能与对卡那霉素的耐药有关。Rv2686c、Rv2687c或Rv2688c的表达与氟喹诺酮耐药之间没有明显相关性。为了探究外排泵耐药机制的细节，需要对外排泵抑制剂、转录调节因子（如whiB7）和其他外排泵基因进行进一步研究。
