Kelly Michael, Cambray Samantha, McCarthy Kelly A, Wang Wenjian, Geisinger Edward, Ortiz-Marquez Juan, van Opijnen Tim, Gao Jianmin
Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States.
Department of Biology, Northeastern University, Boston, Massachusetts 02115, United States.
ACS Infect Dis. 2020 Sep 11;6(9):2410-2418. doi: 10.1021/acsinfecdis.0c00206. Epub 2020 Aug 19.
Colistin is an antibiotic of last resort used to treat infections caused by multidrug-resistant Gram-negative bacterial pathogens. The recent surge in reported cases of colistin-resistant infections urgently calls for fast and reliable diagnostic methods, which can be used for the facile detection and proper treatment of these challenging infections. A major mechanism of colistin resistance involves phosphoethanolamine (PE) modification of lipopolysaccharide (LPS), the molecular target of colistin. This LPS modification mechanism has been recently reported to be transferrable via a plasmid-carried gene, which is particularly concerning as it may readily confer colistin resistance to a wide array of bacterial pathogens. To develop molecular tools to allow facile detection of colistin resistance, we have herein enlisted a novel phage library that incorporates dynamic covalent warheads to recognize PE modifications on bacterial cells. Screening of this chemically modified phage library against colistin-resistant pathogens revealed a number of peptide probes that readily differentiate colistin-resistant bacterial strains from their colistin-susceptible counterparts. With a fluorophore label, these peptide probes selectively stain colistin-resistant bacteria at sub-to-low micromolar concentrations. The bacterial staining is minimally inhibited by the presence of serum proteins or even blood serum. Mechanistic studies indicate that our peptide probes bind colistin-resistant bacteria primarily by targeting PE-modified lipids. However, some species-specific features of the cell surface can also contribute to the peptides' association to bacterial cells. Further elucidation of such cell surface features may give molecular probes with improved species and strain specificity, which will enable bacterial infection diagnosis with high precision.
黏菌素是一种用于治疗由多重耐药革兰氏阴性菌病原体引起的感染的最后手段抗生素。最近报道的耐黏菌素感染病例激增，迫切需要快速可靠的诊断方法，这些方法可用于轻松检测和妥善治疗这些具有挑战性的感染。耐黏菌素的一个主要机制涉及脂多糖（LPS）的磷酸乙醇胺（PE）修饰，而LPS是黏菌素的分子靶点。最近有报道称，这种LPS修饰机制可通过质粒携带的基因进行转移，这尤其令人担忧，因为它可能很容易使多种细菌病原体产生耐黏菌素性。为了开发便于检测耐黏菌素性的分子工具，我们在此利用了一个新型噬菌体文库，该文库包含动态共价弹头以识别细菌细胞上的PE修饰。用这个化学修饰的噬菌体文库对耐黏菌素病原体进行筛选，发现了一些肽探针，这些探针能轻易区分耐黏菌素的细菌菌株与其敏感菌株。通过荧光团标记，这些肽探针在亚微摩尔至低微摩尔浓度下选择性地对耐黏菌素细菌进行染色。血清蛋白甚至血清的存在对细菌染色的抑制作用最小。机理研究表明，我们的肽探针主要通过靶向PE修饰的脂质与耐黏菌素细菌结合。然而，细胞表面的一些物种特异性特征也可能有助于肽与细菌细胞的结合。进一步阐明这些细胞表面特征可能会得到具有更高物种和菌株特异性的分子探针，从而实现高精度的细菌感染诊断。
