Ng Hien Fuh, Ngeow Yun Fong
Dr. Wu Lien-Teh Centre for Research in Communicable Diseases, M. Kandiah Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Selangor, Malaysia.
Department of Pre-clinical Sciences, M. Kandiah Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Selangor, Malaysia.
Microb Drug Resist. 2023 Feb;29(2):41-46. doi: 10.1089/mdr.2022.0068.
Linezolid is one of the antibiotics used to treat the infection. However, linezolid-resistance mechanisms of this organism are not well understood. The objective of this study was to identify possible linezolid-resistance determinants in through characterization of step-wise mutants selected from a linezolid-susceptible strain, M61 (minimum inhibitory concentration [MIC]: 0.25 mg/L). Whole-genome sequencing and subsequent PCR verification of the resistant second-step mutant, A2a(1) (MIC: >256 mg/L), revealed three mutations in its genome, two of which were found in the 23S rDNA (g2244t and g2788t) and another one was found in a gene encoding the fatty-acid-CoA ligase FadD32 (c880t→H294Y). The 23S rRNA is the molecular target of linezolid and mutations in this gene are likely to contribute to resistance. Furthermore, PCR analysis revealed that the c880t mutation in the gene first appeared in the first-step mutant, A2 (MIC: 1 mg/L). Complementation of the wild-type M61 with the pMV261 plasmid carrying the mutant gene caused the previously sensitive M61 to develop a reduced susceptibility to linezolid (MIC: 1 mg/L). The findings of this study uncovered hitherto undescribed mechanisms of linezolid resistance in that may be useful for the development of novel anti-infective agents against this multidrug-resistant pathogen.
利奈唑胺是用于治疗该感染的抗生素之一。然而，这种生物体对利奈唑胺的耐药机制尚未完全了解。本研究的目的是通过对从利奈唑胺敏感菌株M61（最低抑菌浓度[MIC]：0.25mg/L）中筛选出的逐步突变体进行表征，来确定可能的利奈唑胺耐药决定因素。对耐药第二步突变体A2a(1)（MIC：>256mg/L）进行全基因组测序及后续PCR验证，发现其基因组中有三个突变，其中两个位于23S rDNA（g2244t和g2788t），另一个位于编码脂肪酸辅酶A连接酶FadD32的基因中（c880t→H294Y）。23S rRNA是利奈唑胺的分子靶点，该基因中的突变可能导致耐药。此外，PCR分析显示，该基因中的c880t突变首先出现在第一步突变体A2（MIC：1mg/L）中。用携带突变基因的pMV261质粒对野生型M61进行互补，导致先前敏感的M61对利奈唑胺的敏感性降低（MIC：1mg/L）。本研究结果揭示了迄今未描述的该菌对利奈唑胺的耐药机制，这可能有助于开发针对这种多重耐药病原体的新型抗感染药物。
