Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel; Clinical Microbiology Laboratory, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv, Israel.
Int J Antimicrob Agents. 2024 Feb;63(2):107089. doi: 10.1016/j.ijantimicag.2024.107089. Epub 2024 Jan 12.
Aminoglycoside resistance in bacteria is typically conferred by specific drug-modifying enzymes. Infrequently, such resistance is achieved through 16S ribosomal RNA methyltransferases, such as NpmA and KamB encoded by Escherichia coli and Streptoalloteichus tenebrarius, respectively. These enzymes are not widespread and have not been described in Nocardia species to date.
We report the genomic mining of 18 Nocardia wallacei isolates that were found to be specifically and substantially resistant to amikacin.
We identified a gene coding for a protein with very distant homology to NpmA and KamB. However, 3-D modeling revealed that the tertiary structure of these three proteins was highly similar. Cloning and expressing this gene in two susceptible bacteria Nocardia asteroides, and Mycobacterium smegmatis (another Actinobacterium) led to high-level, pan-aminoglycoside resistance in both cases. We named this gene warA (Wallacei Amikacin Resistance A).
This is the first description and experimental characterization of a gene of this family in Nocardia, and the first demonstration that such activity could lead to pan-aminoglycoside resistance in Mycobacteria as well. The discovery of this novel gene has important biotechnology and clinical implications.
细菌中氨基糖苷类药物的耐药性通常由特定的药物修饰酶赋予。不常见的是，这种耐药性是通过 16S 核糖体 RNA 甲基转移酶实现的，例如大肠杆菌和 Streptoalloteichus tenebrarius 分别编码的 NpmA 和 KamB。这些酶并不广泛，迄今为止尚未在诺卡氏菌属中描述过。
我们报告了对 18 株 Wallacei 诺卡氏菌分离株进行基因组挖掘的结果，这些分离株对阿米卡星具有特异性和实质性耐药性。
我们鉴定了一个编码蛋白的基因，该蛋白与 NpmA 和 KamB 具有非常远的同源性。然而，三维建模显示这三种蛋白质的三级结构高度相似。在两种敏感细菌 Nocardia asteroides 和 Mycobacterium smegmatis（另一种放线菌）中克隆和表达该基因，导致这两种情况下均对泛氨基糖苷类药物产生高水平耐药性。我们将该基因命名为 warA（Wallacei Amikacin Resistance A）。
这是首次在诺卡氏菌中描述和实验表征该家族的基因，也是首次证明这种活性可导致分枝杆菌对泛氨基糖苷类药物产生耐药性。该新基因的发现具有重要的生物技术和临床意义。
