Biology of hypervirulent Klebsiella pneumoniae translocation from the gastrointestinal tract

说明. 肺炎克雷伯菌（Kpn）是医院获得性感染的重要来源。由于KPN收购了多个- 另一个令人担忧的问题是， 称为“高毒力”肺炎克雷伯氏菌或hvKpn的菌株，已知其在 社区设置。这些分离株已经获得了一系列毒力因子，这使得它们能够引起 免疫功能正常的个体中的疾病。最近，多起致命的医院疫情与多起- 耐药hvKpn分离株。流行病学研究表明，胃肠道（GI）定植的hvKpn是 一个主要的水库，通过它可以易位到无菌部位，并导致疾病的表现， 殖民地然而，hvKpn肠道定植作为一个易处理的模型尚未成为以往研究的重点 胃肠道（GI）定植和易位不存在。我们最近开发了一种小鼠模型 Kpn和hvKpn GI定殖，而不需要抗生素。我们的易处理模型允许 我们更好地了解Kpn与宿主的动态相互作用，肠道微生物组完整。 此外，还观察到化脓性肝脓肿的发展，这是人类hvKpn感染的标志 在我们的GI殖民模型中。因此，我们认为hvKpn使用特定的途径来促进其表达。 易位，促进其毒力决定因素。这些决定因素可以作为新的目标， 预防疾病状态的发展。最近，通过我们的动物模型， 在GI定植后24小时发生易位。然而，hvKpn所采取的确切路线以及 特化肠上皮细胞（M细胞）的易位仍有待阐明。因此，在目标#1中，我们将执行 体外细胞系测定以确定hvKpn促进其易位所采用的途径。其次，我们将 使用敲除小鼠品系确定宿主M细胞在促进hvKpn易位中的作用。我们的数据表明 hvKpn特异性铁获取分子需氧菌素（iuc）有助于易位过程。 尽管iuc在易位中起作用，但iuc突变体并不完全消除它，这表明其他突变体也可能在易位中起作用。 这些因素对易位至关重要。通过在目标#2中采用体内新的高通量方法，我们将 鉴定促进其易位的推定的hvKpn因子。我们的研究结果不仅提供了一个 了解易位过程，但也确定推定的易位决定因素，这可能是 降低hvKpn疾病负担的潜在目标。

Description. Klebsiella pneumoniae (Kpn) is a significant source of hospital-acquired infections. As Kpn has acquired multi- drug resistance, it has become even more challenging to treat. Another concern is the increase in isolation of strains termed as "hypervirulent" Klebsiella pneumoniae or hvKpn known to cause disease manifestations in a community setting. These isolates have acquired a repertoire of virulence factors, which allow them to cause disease in immunocompetent individuals. Recently, multiple fatal hospital outbreaks have been linked to multi- drug resistant hvKpn isolates. Epidemiological studies suggest that gastrointestinal (GI) colonization of hvKpn is a major reservoir through which it can translocate to sterile sites and cause disease manifestations in the colonized host. However, hvKpn gut colonization has not been the focus of previous studies as a tractable model for gastrointestinal (GI) colonization and translocation did not exist. We recently developed a murine model of Kpn and hvKpn GI colonization, achieved without the requirement of antibiotics. Our tractable model allows us a better understanding of the dynamic interactions of Kpn with the host with an intact gut microbiome. Moreover, development of pyogenic liver abscess a trademark of hvKpn infections in humans was also observed in our GI model of colonization. Thus, we propose that hvKpn uses specific pathways to promote its translocation, facilitated by its virulence determinants. These determinants can serve as novel targets for the prevention of the development of the disease state. More recently, with our animal model, we observed translocation to occur 24 hours post-GI colonization. However, the exact route(s) taken by hvKpn and the role of specialized enterocytes (M-cells) in translocation remains to be elucidated. Thus, in Aim #1, we will carry out in vitro cell line assays to determine the pathway(s) taken by hvKpn to promote its translocation. Secondly, we will determine the host M-cells' role in promoting hvKpn translocation using knockout mice strains. Our data suggest that hvKpn specific iron acquisition molecule aerobactin (iuc) contributes towards the translocation process. Even though iuc plays a role in translocation, an iuc mutant does not entirely abrogate it, suggesting that other factors are critical for translocation. By taking an in vivo novel high-throughput approach in Aim #2, we will identify putative hvKpn factors that promote its translocation. Results from our studies will not only provide an understanding of the translocation process but also identify putative translocation determinants, which could be potential targets to reduce the hvKpn disease burden.