Li Yi, Mishra Nagendra N, Chen Liang, Manna Adhar C, Cheung Ambrose L, Proctor Richard A, Xiong Yan Q
The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, USA.
David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
J Infect Dis. 2024 Dec 31. doi: 10.1093/infdis/jiae640.
Methicillin-resistant Staphylococcus aureus (MRSA) is a leading pathogen causing severe endovascular infections. The prophage-encoded protein Gp05 has been identified as a critical virulence factor that contributes to MRSA persistence during vancomycin (VAN) treatment in an experimental endocarditis model. However, the underlining mechanisms driving this persistence phenotype remain poorly understood.
The current study aimed to elucidate the genetic factors contributing to Gp05-associated MRSA persistence by utilizing RNA sequencing (RNA-seq) on an isogenic MRSA strain set, including a clinical persistent bacteremia isolate (PB 300-169), its isogenic chromosomal gp05 deletion mutant, and gp05-complemented strains.
RNA-seq analysis revealed significantly downregulation of the graSR-vraFG regulatory system and its downstream genes, mprF and dltABCD, in the gp05 deletion mutant compared to the wild-type and gp05-complemented strains. Notably, this downregulation led to a substantial shift in cell membrane composition, with a marked increase in negatively charged phosphatidylglycerol (PG) and a concomitant decrease in positively charged lysyl-PG (LPG). These changes in membrane lipid composition resulted in increased susceptibility of the gp05 deletion mutant to human cationic antimicrobial peptide (CAMP) LL-37, polymorphonuclear neutrophil (PMN) and VAN. Similar findings were observed in an isogenic gp05 overexpression strain set with different genetic background (MRSA USA300 JE2).
These findings suggest that Gp05 plays a pivotal role in MRSA persistence by modulating cell surface components and surface charge. This study provides new insights into the molecular mechanisms underlying Gp05-mediated persistence in MRSA endovascular infections and highlights potential therapeutic targets to combat persistent MRSA infections.
耐甲氧西林金黄色葡萄球菌（MRSA）是引起严重血管内感染的主要病原体。在实验性心内膜炎模型中，原噬菌体编码的蛋白Gp05已被确定为一种关键的毒力因子，它有助于MRSA在万古霉素（VAN）治疗期间持续存在。然而，驱动这种持续存在表型的潜在机制仍知之甚少。
本研究旨在通过对一组同基因MRSA菌株进行RNA测序（RNA-seq），以阐明促成与Gp05相关的MRSA持续存在的遗传因素，该菌株组包括一株临床持续性菌血症分离株（PB 300-169）、其同基因染色体gp05缺失突变体和gp05互补菌株。
RNA-seq分析显示，与野生型和gp05互补菌株相比，gp05缺失突变体中graSR-vraFG调节系统及其下游基因mprF和dltABCD显著下调。值得注意的是，这种下调导致细胞膜组成发生实质性变化，带负电荷的磷脂酰甘油（PG）显著增加，同时带正电荷的赖氨酰-PG（LPG）减少。膜脂质组成的这些变化导致gp05缺失突变体对人阳离子抗菌肽（CAMP）LL-37、多形核中性粒细胞（PMN）和VAN的敏感性增加。在具有不同遗传背景的同基因gp05过表达菌株组（MRSA USA300 JE2）中也观察到了类似的结果。
这些发现表明，Gp05通过调节细胞表面成分和表面电荷在MRSA持续存在中起关键作用。本研究为Gp05介导的MRSA血管内感染持续存在的分子机制提供了新的见解，并突出了对抗持续性MRSA感染的潜在治疗靶点。
