David Braley Center for Antibiotic Discovery, Michael G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
ACS Infect Dis. 2023 Jul 14;9(7):1408-1423. doi: 10.1021/acsinfecdis.3c00167. Epub 2023 Jun 6.
Traditional antibacterial screens rely on growing bacteria in nutrient-replete conditions which are not representative of the natural environment or sites of infection. Instead, screening in more physiologically relevant conditions may reveal novel activity for existing antibiotics. Here, we screened a panel of antibiotics reported to lack activity against the opportunistic Gram-negative bacterium, , under low-nutrient and low-iron conditions, and discovered that the glycopeptide vancomycin inhibited the growth of at low micromolar concentrations through its canonical mechanism of action, disruption of peptidoglycan crosslinking. Spontaneous vancomycin-resistant mutants underwent activating mutations in the sensor kinase of the two-component CpxSR system, which induced cross-resistance to almost all classes of β-lactams, including the siderophore antibiotic cefiderocol. Other mutations that conferred vancomycin resistance mapped to WapR, an α-1,3-rhamnosyltransferase involved in lipopolysaccharide core biosynthesis. A WapR P164T mutant had a modified LPS profile compared to wild type that was accompanied by increased susceptibility to select bacteriophages. We conclude that screening in nutrient-limited conditions can reveal novel activity for existing antibiotics and lead to discovery of new and impactful resistance mechanisms.
传统的抗菌筛选依赖于在营养丰富的条件下培养细菌，而这些条件并不代表自然环境或感染部位。相反，在更具生理相关性的条件下进行筛选可能会发现现有抗生素的新活性。在这里，我们在低营养和低铁条件下筛选了一组据报道对机会性革兰氏阴性菌 没有活性的抗生素，发现糖肽万古霉素通过其破坏肽聚糖交联的典型作用机制，以低微摩尔浓度抑制 的生长。自发产生的万古霉素抗性突变体在双组分 CpxSR 系统的传感器激酶中发生激活突变，这诱导了对几乎所有β-内酰胺类药物的交叉耐药性，包括铁载体抗生素头孢他啶。赋予万古霉素抗性的其他突变映射到 WapR，这是一种参与脂多糖核心生物合成的α-1,3-鼠李糖基转移酶。与野生型相比，WapR P164T 突变体的 LPS 图谱发生了改变，并且对选择噬菌体的敏感性增加。我们得出的结论是，在营养受限的条件下进行筛选可以揭示现有抗生素的新活性，并发现新的、有影响力的耐药机制。
