Characterization of a novel murine model of central nervous system catheter infec

描述(申请人提供)：脑脊液(CSF)分流感染是儿科人群脑积水治疗中常见和严重的并发症，据报道发病率为5-15%1。引起这些中枢神经系统(CNS)导管感染的最常见的微生物，表皮葡萄球菌和金黄色葡萄球菌，都已知形成生物膜2，3。这些生物膜是聚集在导管表面的细菌细胞的有组织群落，封闭在自我产生的基质中保护微生物。生物膜逃避宿主免疫反应和抗菌药物的能力使非手术治疗中枢神经系统导管感染变得困难，因此目前需要拔除导管才能有效地治疗这些感染。虽然微生物学家正在广泛地研究生物膜形成所需细菌的生长特征和其他适应能力，但对宿主与生物膜的相互作用知之甚少，特别是关于导管生物膜感染的免疫反应。为了探讨中枢神经系统导管感染的神经免疫反应，我建立了一种新的小鼠中枢神经系统导管感染模型。这项技术导致持续的导管相关性金黄色葡萄球菌感染和脑室炎，类似于人类脑室分流感染的后遗症。该模型的建立为利用基因工程敲除或转基因小鼠品系识别宿主对CNS生物膜免疫应答中的重要因素提供了有力的工具。本研究的目的是利用这种中枢神经系统导管感染模型，通过研究细菌生长的动力学和宿主的天然免疫反应，来表征感染金黄色葡萄球菌的中枢神经系统生物膜的宿主免疫反应。了解神经免疫系统和感染导管上形成的生物膜之间的相互作用将使我们能够在未来的研究中探索针对这些感染的新的管理策略。这一K08建议的总体假设是，宿主大脑中的先天免疫反应因中枢神经系统导管的生物膜定植而主动减弱。为了验证这一假设，我们将进行两个特定目标的实验。在目标1中，我们将在中枢神经系统导管感染的小鼠模型中表征细菌生长动力学和先天免疫反应。在目标2中，我们将通过使用一株SARA表达缺失的同基因突变的金黄色葡萄球菌来确定细菌调节因子在中枢神经系统导管感染发展中的作用，该突变株在生物被膜形成中发挥作用。最后，候选人是一名儿科传染病专家，长期对中枢神经系统感染和宿主反应在儿科感染中的作用感兴趣。她是一位备受支持的候选人，热衷于成为一名内科科学家，并将从临床科学家发展奖中受益匪浅。 公共卫生相关性：在儿童人群中，脑脊液分流感染是治疗脑积水的常见和严重的并发症。在这项提议中，我们将研究免疫系统和中枢神经系统内这些导管上形成的生物膜之间的相互作用。这些研究将提供关于中枢神经系统内这种生物被膜感染的免疫反应的有价值的信息，可能导致用于管理这些感染的新的诊断和治疗工具。

DESCRIPTION (provided by applicant): Cerebrospinal fluid (CSF) shunt infections are a frequent and serious complication in the treatment of hydrocephalus in the pediatric population, with a reported incidence of 5-15%1. The most common organisms responsible for these central nervous system (CNS) catheter infections, Staphylococcus epidermidis and Staphylococcus aureus, are both known to form biofilms2,3. These biofilms are organized communities of bacterial cells that aggregate on the catheter surface, enclosed in a self-produced matrix that protects the organisms. The biofilm's ability to evade the host immune response and antimicrobial agents makes it difficult to manage CNS catheter infections non-surgically, such that catheter removal is currently required to effectively treat these infections. While the growth characteristics and other adaptations of the bacteria required for biofilm formation are being extensively investigated by microbiologists, very little is known about the host interaction with the biofilm, particularly with regard to the immune response to catheter biofilm infections. To explore the neuroimmune response to CNS catheter infections, I have developed a novel model of CNS catheter infection in the mouse. This technique results in a consistent catheter-associated infection with S. aureus and ventriculitis, similar to the sequelae seen in humans with ventricular shunt infections. Establishment of this model provides a powerful tool to identify important factors in the host immune response to CNS biofilms through the use of genetically engineered knockout or transgenic mouse strains. The objective of this study is to utilize this model of CNS catheter infection to characterize the host immune response to a CNS biofilm infection with S. aureus by investigating the kinetics of bacterial growth and the host innate immune response in this setting. Understanding the interactions between the neuroimmune system and the biofilms that form on infected catheters will allow us to explore novel management strategies for these infections in future studies. The overall hypothesis of this K08 proposal is that the host innate immune response in the brain is actively attenuated in response to biofilm colonization of a CNS catheter. To test this hypothesis, we will perform experiments outlined in two specific aims. In Aim 1, we will characterize the bacterial growth kinetics and innate immune response in a murine model of CNS catheter infection. In Aim 2, we will define the role of bacterial regulatory factors in the development of CNS catheter infection by using an isogenic mutant S. aureus strain, deficient in sarA expression, which is known to play a role in biofilm formation. Finally, the candidate is a pediatric infectious disease specialist with a long-standing interest in CNS infections and the role of the host response in pediatric infections. She is a well-supported candidate with an avid interest in becoming a physician scientist who will benefit highly from a Clinical Scientist Development Award. PUBLIC HEALTH RELEVANCE: Cerebrospinal fluid shunt infections are a frequent and serious complication in the treatment of hydrocephalus in the pediatric population. In this proposal, we will study the interactions between the immune system and the biofilms that form on these catheters within the central nervous system. These studies will provide valuable information about the immune response to this biofilm infection within the CNS, potentially leading to novel diagnostic and therapeutic tools for use in management of these infections.