Proteus mirabilis swarming: Initiation and role during urinary tract infection

描述（由申请方提供）：导管相关尿路感染（CANTI）是最常见的医院获得性感染，主要由奇异变形杆菌引起。该物种具有独特的分化能力，能够分化成在导管表面迁移的群细胞， 进入泌尿道，尽管进行了抗生素治疗，奇异变形杆菌仍能持续存在，并经常导致形成疼痛的尿路结石。因此，奇异变形杆菌群集是一个迷人的和医学相关的问题，自发现以来一直困扰着科学家。在理解触发奇异变形杆菌群集运动的特定线索和条件以及群细胞在UTI期间的作用方面存在根本性差距。解决这一差距有可能指导导管或涂层的设计，以防止奇异变形杆菌进入尿路，并为破坏持续性和严重感染提供新的目标，减少尿路感染和相关并发症的负担。核心假设是奇异变形杆菌群细胞分化和群集运动是响应于特定的环境线索而启动的，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，将通过追求两个特定目标来测试该假设：1）识别触发群集的特定因素和条件，并确定细菌群体如何感知这些因素，以及2）定义群细胞分化和群集触发因素在UTI的持续性和严重性中的作用。在第一个目标下，候选人已经确定了触发已充分表征的奇异变形杆菌菌株HI 4320群集的因素，其基础是在通常不允许的条件下促进群集的能力。使用其中碳源、氮源和pH变化的培养基配方来确定启动群集运动的最佳条件和最低要求。还建立了一个转座子库，并将进行筛选，以确定失去对触发因素作出反应的能力的突变体，从而确定参与感知和对触发因素作出反应的基因和途径。在第二个目标下，将利用已建立的上行性UTI的CBA/J模型和生物光子成像来确定UTI期间群细胞的频率和分布。也将使用CBA/J模型和在第一个目标中构建的突变体来解决群细胞和群集触发器对UTI的建立、持续性和严重性的贡献。这项研究意义重大，因为它将深入了解细菌如何决定在琼脂表面和感染宿主期间执行协调的多细胞功能。这项研究还将有助于对细菌如何感知和与环境相互作用以及细菌代谢如何影响发病机制的一般理解。最终，这些知识有可能为导管设计和治疗策略提供信息，以减少PITTI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.