CSIR-Institute of Genomics and Integrative Biology, New Delhi, India; Academy of Scientific and Innovative Research, Ghaziabad, India.
CSIR-Institute of Genomics and Integrative Biology, New Delhi, India; Academy of Scientific and Innovative Research, Ghaziabad, India.
J Glob Antimicrob Resist. 2020 Dec;23:359-369. doi: 10.1016/j.jgar.2020.10.006. Epub 2020 Nov 10.
Modulation of methylation pattern through mutations in ribosomal methyltransferases is a key mechanism of bacterial drug resistance. However, RsmG (GidB), which specifically methylates G527 in 16S rRNA, remains the only conserved methyltransferase known to be associated with low-level drug resistance in mycobacterial isolates. The mycobacterial RsmE homologue methylates U1498 in 16S rRNA in a highly specific manner. U1498 lies in the vicinity of the binding site for various aminoglycosides in the ribosome. However, the association of methylation at U1498 with altered drug response remains poorly understood.
A deletion mutant of the RsmE homologue in Mycobacterium smegmatis was generated by a suicidal vector strategy and drug susceptibility assays were performed on wild-type, knockout and complemented strains with varying concentrations of ribosomal- and non-ribosomal-targeting drugs.
Deletion of the RsmE homologue of M. smegmatis led to an at least two-fold increase in the minimum inhibitory concentrations (MICs) of aminoglycosides that bind in the decoding centre proximal to U1498 in the 30S subunit. The change in MICs was highly specific and reproducible and did not show any cross-resistance to other drug classes. Surprisingly, Rv2372c, the RsmE homologue of Mycobacterium tuberculosis, has the largest number of mutations among conserved ribosomal methyltransferases, after gidB, highlighting the role of mutations in RsmE methyltransferase as a key emerging mechanism of resistance in clinical strains.
We present the first evidence of an association of methylation of U1498 in 16S rRNA with development of low-level resistance in mycobacteria that must be tackled in a timely manner.
通过核糖体甲基转移酶的突变来调节甲基化模式是细菌耐药性的一个关键机制。然而，RsmG（GidB）是唯一已知与分枝杆菌分离株中低水平药物耐药性相关的保守甲基转移酶，它特异性地甲基化 16S rRNA 中的 G527。分枝杆菌 RsmE 同源物以高度特异性的方式甲基化 16S rRNA 中的 U1498。U1498 位于核糖体中各种氨基糖苷类药物结合位点的附近。然而，U1498 甲基化与改变药物反应的关联仍知之甚少。
通过自杀载体策略生成了分枝杆菌耻垢亚种中 RsmE 同源物的缺失突变体，并对野生型、敲除和互补菌株进行了药物敏感性测定，使用了不同浓度的核糖体和非核糖体靶向药物。
分枝杆菌耻垢亚种 RsmE 同源物的缺失导致与 U1498 在 30S 亚基中接近解码中心结合的氨基糖苷类药物的最低抑菌浓度（MIC）至少增加了两倍。MIC 的变化具有高度特异性和可重复性，并且与其他药物类别没有任何交叉耐药性。令人惊讶的是，分枝杆菌结核分枝杆菌的 Rv2372c 是保守核糖体甲基转移酶中突变数量最多的，仅次于 gidB，这突出了 RsmE 甲基转移酶突变作为临床菌株中耐药性出现的关键新兴机制的作用。
我们首次提出了 16S rRNA 中 U1498 甲基化与分枝杆菌低水平耐药性发展之间的关联证据，必须及时解决这一问题。
