Proteus mirabilis swarming: Initiation and role during urinary tract infection

描述(申请人提供)：导管相关性尿路感染(CAUTI)是最常见的医院获得性感染，主要由奇异变形杆菌引起。这一物种具有独特的分化能力，可以分化为穿过导管表面迁移的群体细胞，并获得 进入尿路，即使接受抗生素治疗，奇异肺炎杆菌仍可在那里存活，并经常导致疼痛的尿路结石形成。因此，奇异P.mirabilis的成群是一个令人着迷且与医学相关的问题，自发现以来一直困扰着科学家。在对触发奇异疟原虫成群运动的特定线索和条件以及群体细胞在尿路感染中的作用的理解上存在着根本性的差距。解决这一差距有可能指导导管或涂层的设计，以防止奇异肺炎杆菌进入尿路，并为中断持续和严重的感染提供新的靶点，减少CAUTI和相关并发症的负担。中心假说是奇异变形杆菌的群体细胞分化和群体运动是对特定环境线索的反应，并影响UTI的建立、持续和严重程度。在大量初步数据的指导下，将通过追求两个具体目标来检验这一假说：1)确定触发集聚的特定因素和条件，并确定这些因素如何被细菌群体感知；2)确定群体细胞分化和集聚触发因素在尿路感染持久性和严重性中的作用。在第一个目标下，基于在通常不允许的条件下促进集群的能力，候选人已经确定了触发特征良好的奇异P.mirabilis菌株HI4320集群的因素。碳源、氮源和pH不同的基质配方正被用来确定启动集群运动的最佳条件和最低要求。还创建了一个转座子库，并将对其进行筛选，以识别已经失去了对触发事件做出反应的群聚能力的突变体，从而能够识别与感知和响应触发事件有关的基因和途径。在第二个目标下，将利用建立的CBA/J上行尿路感染模型和生物光子成像来确定尿路感染期间群体细胞的频率和分布。群集性细胞和群集性触发因素对UTI的建立、持久性和严重性的贡献也将通过第一个目标中构建的CBA/J模型和突变体来解决。这项拟议的研究意义重大，因为它将为细菌决定如何在琼脂表面和感染宿主期间执行协调的多细胞功能提供洞察力。这项研究还将有助于全面了解细菌如何感知环境并与环境相互作用，以及细菌代谢如何影响致病机理。最终，这些知识有可能为导管设计和治疗策略提供信息，以减轻CAUTI的负担。

DESCRIPTION (provided by applicant): Catheter-associated urinary tract infection (CAUTI) is the most common hospital-acquired infection, largely due to Proteus mirabilis. This species has the unique ability to differentiate into swarm cells that migrate across catheter surfaces and gain entry to the urinary tract, where P. mirabilis can persist despite antibiotic treatment and frequently results in formation of painful urinary stones. P. mirabilis swarming is therefore a fascinating and medically-relevant problem that has perplexed scientists since its discovery. There is a fundamental gap in understanding of the specific cues and conditions that trigger P. mirabilis swarming motility, as well as the role of swarm cells during UTI. Addressing this gap has the potential to guide design of catheters or coatings that prevent entry of P. mirabilis into the urinary tract and provide new targets for disruption of persistent and severe infections, reducing the burden of CAUTI and associated complications. The central hypothesis is that Proteus mirabilis swarm cell differentiation and swarming motility are initiated in response to specific environmental cues and influence the establishment, persistence, and severity of UTI. Guided by substantial preliminary data, this hypothesis will be tested by pursuing two specific aims: 1) Identify specific factors and conditions that trigger swarming and determine how these factors are sensed by the bacterial population, and 2) Define the role of swarm cell differentiation and swarming triggers in the persistence and severity of UTI. Under the first aim, factors that trigger swarming by the well-characterized P. mirabilis strain HI4320 are already being identified by the candidate, based on the ability to promote swarming under normally non-permissive conditions. Media formulations in which carbon source, nitrogen source, and pH are varied are being used to determine the optimal conditions and minimal requirements for initiation of swarming motility. A transposon library has also been created and will be screened to identify mutants that have lost the ability to swarm in response to triggers, allowing for identification of genes and pathways involved in sensing and responding to the triggers. Under the second aim, the established CBA/J model of ascending UTI and biophotonic imaging will be utilized to determine the frequency and distribution of swarm cells during UTI. The contribution of swarm cells and swarming triggers to the establishment, persistence, and severity of UTI will also be addressed using the CBA/J model and mutants constructed in the first aim. The proposed research is significant because it will provide insight into how bacteria decide to perform coordinated multicellular functions, both on an agar surface and during infection of a host. This research will also contribute to a general understanding of how bacteria sense and interact with their environment, and how bacterial metabolism impacts pathogenesis. Ultimately, such knowledge has the potential to inform catheter design and therapeutic strategies for reducing the burden of CAUTI.