Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo, 11562, Egypt.
Natural Products Research Department, National Centre for Radiation Research and Technology, Egyptian Atomic Energy Authority, Cairo, Egypt.
Microb Pathog. 2024 Aug;193:106762. doi: 10.1016/j.micpath.2024.106762. Epub 2024 Jun 25.
Enterococcus faecalis is a troublesome nosocomial pathogen that acquired resistance to most available antimicrobial agents. Antivirulence agents represent an unconventional treatment approach. Here, transcription factor decoy (TFD)-loaded cationic liposomes (TLL) were developed as an inhibitor of the Fsr quorum-sensing system and its associated virulence traits, in E. faecalis. The consensus sequence of the FsrA binding site was found conserved among 651 E. faecalis annotated genomes. The TFD was synthesized as an 82 bp DNA duplex, containing the conserved binding sequence, and loaded onto cationic liposomes. The optimum loading capacity, mean particle size, and zeta potential of the TLL were characterized. The developed TLL lacked any effect on E. faecalis growth and significantly inhibited the in vitro production of the proteolytic enzymes controlled by the Fsr system; gelatinase and serine protease, in a concentration-dependent manner. This inhibition was accompanied by a significant reduction in the transcription levels of FsrA-regulated genes (fsrB, gelE, and sprE). The developed TLL were safe as evidenced by the nonhemolytic effect on human RBCs and the negligible cytotoxicity on human skin fibroblast cells. Moreover, in the larvae infection model, TLL displayed a significant abolish in the mortality rates of Galleria mellonella larvae infected with E. faecalis. In conclusion, the developed TLL offer a new safe strategy for combating E. faecalis infection through the inhibition of quorum-sensing-mediated virulence; providing a platform for the development of similar agents to combat many other pathogens.
粪肠球菌是一种棘手的医院获得性病原体，它对大多数可用的抗菌药物都产生了耐药性。抗病毒药物代表了一种非传统的治疗方法。在这里，转录因子诱饵（TFD）负载的阳离子脂质体（TLL）被开发为 Fsr 群体感应系统及其相关毒力特性的抑制剂，在粪肠球菌中。FsrA 结合位点的共识序列在 651 个粪肠球菌注释基因组中被发现保守。TFD 被合成为含有保守结合序列的 82 bp DNA 双链体，并负载到阳离子脂质体上。TLL 的最佳载药能力、平均粒径和 Zeta 电位进行了表征。所开发的 TLL 对粪肠球菌的生长没有任何影响，并且以浓度依赖的方式显著抑制了由 Fsr 系统控制的蛋白酶的体外产生；明胶酶和丝氨酸蛋白酶。这种抑制伴随着 FsrA 调节基因（fsrB、gelE 和 sprE）转录水平的显著降低。所开发的 TLL 是安全的，这一点从它们对人 RBC 没有溶血作用和对人皮肤成纤维细胞的细胞毒性可以忽略不计得到证明。此外，在幼虫感染模型中，TLL 显著降低了感染粪肠球菌的家蚕幼虫的死亡率。总之，所开发的 TLL 通过抑制群体感应介导的毒力为对抗粪肠球菌感染提供了一种新的安全策略；为开发类似的药物来对抗许多其他病原体提供了一个平台。
