Molecular Pathogenesis of Klebsiella Pneumoniae

描述(申请人提供)：肺炎克雷伯氏菌是一种机会致病菌，常与住院患者的呼吸道和尿路感染有关。此外，它是慢性酗酒者肺炎的主要原因，也与社区获得性肺炎有关。感染尤其难以治疗，因为大多数临床分离株对几种抗生素表现出抗药性，导致治疗失败。在人类呼吸道中，肺炎克雷伯菌可以作为生长在肺组织上的生物膜存在。这些细菌产生大量的酸性多糖胶囊，已被证明具有抗吞噬性能，该胶囊被认为是一个重要的毒力因素。然而，对这些细菌产生的其他毒力决定因素知之甚少，这些决定因素使它们能够在扰动的上皮组织上定居和生长，入侵血液，并成功克服宿主防御机制。在这项建议中，我们描述了继续我们对肺炎克雷伯菌分子致病机制的研究。我们将使用涂有人类来源的细胞外基质的流动生物膜室来确定菌毛类型和其他基因产物在这些生物表面形成生物膜的作用。在补充研究中，将利用急性感染的小鼠模型来检查假定的毒力因子在体内的作用。在许多其他致病细菌中，毒力因子表达的遗传调控涉及一个复杂的调控网络或调节子。在这项建议中，我们描述了两系列研究，以检查调节因子在影响细菌在体内引起感染和在体外人类基质上生长的能力方面发挥重要作用。这些调控基因的靶点将被确定。此外，像许多其他肠道细菌一样，肺炎克雷伯菌有能力产生几种不同类型的菌毛或菌毛。不同菌毛类型的协同生产在任何细菌物种中都没有被详细研究过。分离导致至少两种菌毛表达变化的突变将使我们能够开始表征菌毛调节子。综上所述，本研究的目的是阐明菌毛在肺炎克雷伯菌致病机制中的作用，研究影响毒力的调控途径，并确定毒力基因在生物膜生长过程中的表达。公共卫生相关性：该项目调查肺炎克雷伯菌引起呼吸道感染的机制。这些细菌经常会导致住院患者的呼吸道感染，

DESCRIPTION (provided by applicant): Klebsiella pneumoniae is an opportunistic pathogen frequently implicated in respiratory and urinary tract infections of hospitalized patients. In addition, it is a leading cause of pneumonia in chronic alcoholics and has also been associated with community acquired pneumonia. Infections are particularly difficult to treat since most clinical isolates exhibit resistance to several antibiotics leading to treatment failure. In the human respiratory tract it has been suggested that K. pneumoniae can exist as a biofilm growing on lung tissue. These bacteria produce copious amounts of an acidic polysaccharide capsule that has been shown to possess antiphagocytic properties and the capsule is believed to be an important virulence factor. However, relatively little is known about other virulence determinants produced by these bacteria which allow them to colonize and grow on perturbed epithelial tissues, invade into the bloodstream and successfully overcome host defense mechanisms. In this proposal we describe studies to continue our investigations into the molecular pathogenetic mechanisms of K. pneumoniae. We will use flow-through biofilm chambers coated with human-derived extracellular matrices to determine the role of fimbrial types and other gene products in forming a biofilm on these biotic surfaces. In complementary studies a murine model of acute infection will be utilized to examine the role of putative virulence factors in vivo. In many other pathogenic bacteria the genetic regulation of virulence factor expression involves a complex regulatory network or regulon. We describe in this proposal two series of studies to examine regulators that play an important role in influencing the ability of the bacteria to cause infections in vivo and grow on human matrices in vitro. The targets of these regulatory genes will be determined. In addition, like many other enteric bacteria, K. pneumoniae posses the ability to produce several different types of fimbriae or pili. The coordinate production of distinct fimbrial types has not been investigated in detail in any bacterial species. The isolation of mutations that cause alteration in at least two types of fimbrial expression will allow us to begin to characterize the fimbrial regulon. In summary the aims of this proposal are to elucidate the role of fimbriae in K. pneumoniae pathogenesis, to investigate the regulatory pathways affecting virulence, and to define virulence gene expression during biofilm growth. PUBLIC HEALTH RELEVANCE: This project investigates mechanisms used by the bacterium Klebsiella pneumoniae to cause infections of the airways. These bacteria frequently cause airway infections in hospitalized patients,