Dynamics of Pseudomonas aeruginosa During Bacteremia

铜绿假单胞菌（PA）是血流感染的第三大常见革兰氏阴性病原体， 这些感染的粗死亡率为39%。尽管其频率和严重性， 与肺炎、烧伤感染和肺炎相比，对PA血流感染的了解相对较少。 角膜炎。为了研究PA血流感染的发病机制，我们使用了小鼠模型，其中 尾静脉注射条形码细菌文库。我们的初步实验 意想不到的发现首先，在大约一半的重症菌血症小鼠中， 散布在整个身体的是几个细菌细胞的后代，这表明只有一小部分细菌细胞， 最初接种物中的PA数量持续存在并传播，导致严重疾病。第二，PA 血液中的细菌通过一个狭窄的瓶颈迁移到胆囊，胆囊是一个保护性的小生境， 允许少量的PA复制到极高的数量。从那里，这些 只有少数PA细菌在肠道内播种，可能是通过胆总管。这 这一发现在其他报告的背景下特别有趣，这些报告表明PA能够从 肠道进入血液总之，这些观察结果提出了一个有趣的假设， 从血液到肠道再回到血液中的PA可能会产生"正反馈"， 胆囊在其中充当PA数字的放大器。在本申请中，我们提出解决 这一限制，并直接测试我们的假设，通过执行以下具体目标：（1）表征 PA血流感染过程中的细菌动力学。(2)确定干预措施是否 干扰PA通过肠道的转运改善血流感染的结果。完成 这些目标有可能揭示导致不良结局的新的致病机制 在PA血流感染中观察到。这些研究的影响有三个方面：（一）它们可以提供一个 研究PA以外的细菌引起的血流感染的发病机制的基本原理;（ii） 获得的知识可以作为基础和理由，进行更昂贵和更艰苦的研究， PA血流感染的人;和（iii）这些研究可能为新的治疗干预提供信息， 降低目前与PA菌血症相关的高死亡率。

Pseudomonas aeruginosa (PA) is the third most common gram-negative etiology of bloodstream infections, and these infections are associated with a crude mortality rate of 39%. Despite their frequency and severity, PA bloodstream infections are relatively poorly understood compared to pneumonia, burn infections, and keratitis. To investigate the pathogenesis of PA bloodstream infections, we have used a mouse model in which the tail vein is injected with a library of barcoded bacteria. Our preliminary experiments yielded several unexpected findings. First, in approximately half of severely ill bacteremic mice, the PA bacteria found disseminated throughout the body were descendants of just a few bacterial cells, suggesting that only a small number of the PA in the initial inoculum persisted and disseminated to cause severe disease. Second, PA bacteria in the blood migrated through a tight bottleneck to the gallbladder, which was a protective niche that allowed for a small number of PA to replicate to extremely high numbers. From there, these descendants of just a few PA bacteria seeded the intestines, presumably by passing through the common bile duct. This finding is particularly interesting in the context of other reports suggesting that PA is capable of migrating from the intestines to the bloodstream. Together, these observations suggest the intriguing hypothesis that spread of PA from the bloodstream to the intestines and back to the bloodstream may generate a "positive feedback loop" in which the gallbladder serves as an amplifier of PA numbers. In this application, we propose to address this limitation and directly test our hypothesis by performing the following specific aims: (1) Characterize bacterial dynamics over the course of PA bloodstream infections. (2) Determine whether interventions that disrupt PA transit through the intestines improve outcomes in bloodstream infections. Completion of these aims has the potential to uncover novel pathogenic mechanisms that contribute to the poor outcomes observed in PA bloodstream infections. The impact of these studies is three-fold: (i) they may provide a rationale for examining the pathogenesis of bloodstream infections caused by bacteria other than PA; (ii) the knowledge gained may be used as a foundation and justification for costlier and more laborious studies in humans with PA bloodstream infections; and (iii) these studies may inform novel therapeutic interventions that lower the unacceptably high mortality rates currently associated with PA bacteremia.