Zhu Yefei, Xiong Yan Q, Sadykov Marat R, Fey Paul D, Lei Mei G, Lee Chia Y, Bayer Arnold S, Somerville Greg A
Department of Veterinary and Biomedical Sciences, University of Nebraska, 155 VBS, Fair St. and East Campus Loop, Lincoln, NE 68583-0905, USA.
Infect Immun. 2009 Oct;77(10):4256-64. doi: 10.1128/IAI.00195-09. Epub 2009 Aug 10.
Staphylococci are the leading causes of endovascular infections worldwide. Commonly, these infections involve the formation of biofilms on the surface of biomaterials. Biofilms are a complex aggregation of bacteria commonly encapsulated by an adhesive exopolysaccharide matrix. In staphylococci, this exopolysaccharide matrix is composed of polysaccharide intercellular adhesin (PIA). PIA is synthesized when the tricarboxylic acid (TCA) cycle is repressed. The inverse correlation between PIA synthesis and TCA cycle activity led us to hypothesize that increasing TCA cycle activity would decrease PIA synthesis and biofilm formation and reduce virulence in a rabbit catheter-induced model of biofilm infection. TCA cycle activity can be induced by preventing staphylococci from exogenously acquiring a TCA cycle-derived amino acid necessary for growth. To determine if TCA cycle induction would decrease PIA synthesis in Staphylococcus aureus, the glutamine permease gene (glnP) was inactivated and TCA cycle activity, PIA accumulation, biofilm forming ability, and virulence in an experimental catheter-induced endovascular biofilm (endocarditis) model were determined. Inactivation of this major glutamine transporter increased TCA cycle activity, transiently decreased PIA synthesis, and significantly reduced in vivo virulence in the endocarditis model in terms of achievable bacterial densities in biofilm-associated cardiac vegetations, kidneys, and spleen. These data confirm the close linkage of TCA cycle activity and virulence factor production and establish that this metabolic linkage can be manipulated to alter infectious outcomes.
葡萄球菌是全球血管内感染的主要病因。通常情况下，这些感染涉及生物材料表面生物膜的形成。生物膜是细菌的复杂聚集体，通常被粘性胞外多糖基质包裹。在葡萄球菌中，这种胞外多糖基质由多糖细胞间粘附素（PIA）组成。当三羧酸（TCA）循环受到抑制时，PIA得以合成。PIA合成与TCA循环活性之间的负相关关系使我们推测，在兔导管诱导的生物膜感染模型中，提高TCA循环活性会减少PIA合成和生物膜形成，并降低毒力。通过阻止葡萄球菌从外源获取生长所需的TCA循环衍生氨基酸，可以诱导TCA循环活性。为了确定TCA循环诱导是否会减少金黄色葡萄球菌中的PIA合成，我们使谷氨酰胺通透酶基因（glnP）失活，并测定了TCA循环活性、PIA积累、生物膜形成能力以及在实验性导管诱导的血管内生物膜（心内膜炎）模型中的毒力。这种主要谷氨酰胺转运体的失活增加了TCA循环活性，短暂降低了PIA合成，并在生物膜相关心脏赘生物、肾脏和脾脏中可达到细菌密度方面，显著降低了心内膜炎模型中的体内毒力。这些数据证实了TCA循环活性与毒力因子产生之间的紧密联系，并确定这种代谢联系可以被操纵以改变感染结果。
