In a loss-of-viability screen of small molecules against methicillin-resistant Staphylococcus aureus (MRSA) USA300, we found a small molecule, designated DNAC-2, which has an MIC of 8 μg ml^-1. DNAC-2 is a quinolinol derivative that is bactericidal at 2X MIC. Macromolecular synthesis assays at 2 × MIC of DNAC-2 revealed inhibition of DNA, cell wall, RNA and protein synthesis within fifteen to thirty minutes of treatment when compared to the untreated control. Transmission electron microscopy of DNAC-2-treated cells revealed a significantly thicker cell wall and impaired daughter cell separation. Exposure of USA300 cells to 1 × MIC of DNAC-2 resulted in mislocalization of PBP2 away from the septum in an FtsZ-independent manner. In addition, membrane localization with FM4-64, as well as depolarization study with DiOC₂ and lipophilic cation TPP+ displayed membrane irregularities and rapid membrane depolarization, respectively, in DNAC-2-treated cells vs -untreated control. However, DNAC-2 exhibited almost no toxicity toward eukaryotic membranes. Notably, DNAC-2 drives energy generation toward substrate level phosphorylation and the bacteria become more sensitive to DNAC-2 under anaerobic conditions. We propose that DNAC-2 affects USA300 by targeting the membrane, leading to partial membrane depolarization and subsequently affecting aerobic respiration and energy-dependent functional organization of macromolecular biosynthetic pathways. The multiple effects may have the desirable consequence of limiting the emergence of resistance to DNAC-2.

中文翻译：

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一种基于喹啉的小分子，具有抗 MRSA 活性，可靶向细菌膜并促进发酵代谢。

在针对耐甲氧西林金黄色葡萄球菌 (MRSA) USA300 的小分子活性丧失筛选中，我们发现了一种小分子，命名为 DNAC-2，其 MIC 为 8 μg ml ^-1. DNAC-2 是一种喹啉醇衍生物，在 2X MIC 下具有杀菌作用。与未处理的对照相比，DNAC-2 的 2 × MIC 的大分子合成测定显示，在处理后的 15 到 30 分钟内，DNA、细胞壁、RNA 和蛋白质合成受到抑制。DNAC-2 处理的细胞的透射电子显微镜显示细胞壁明显增厚和子细胞分离受损。USA300 细胞暴露于 1 × MIC 的 DNAC-2 导致 PBP2 以不依赖 FtsZ 的方式从隔膜错误定位。此外，使用 FM4-64 进行膜定位，以及使用 DiOC _{2进行去极化研究}和亲脂性阳离子 TPP+ 分别在 DNAC-2 处理的细胞与未处理的对照细胞中表现出膜不规则性和快速膜去极化。然而，DNAC-2 对真核细胞膜几乎没有毒性。值得注意的是，DNAC-2 将能量产生推向底物水平的磷酸化，并且细菌在厌氧条件下对 DNAC-2 变得更加敏感。我们提出 DNAC-2 通过靶向膜影响 USA300，导致部分膜去极化并随后影响有氧呼吸和大分子生物合成途径的能量依赖性功能组织。多重效应可能具有限制对 DNAC-2 抗性出现的理想结果。