D-serine/DsdCXA Control of E. coli Uropathogenesis

描述(申请人提供)：大肠埃希氏菌是社区获得性尿路感染(UTI)的最常见原因，也是医院内UTI和败血症的主要原因。据估计，美国每年有800万人次因尿路感染就诊，与此相关的发病率和费用也很高(&gt；10亿美元)。我们测试了一种假设，即通过将尿毒症大肠杆菌CFT073菌株与大肠杆菌实验室菌株MG1655或O157：H7菌株EDL933进行比较，可以鉴定出与肾盂肾炎和败血症等危及生命的大肠杆菌肠外感染有关的毒力基因。我们确定了&gt；300个CFT073特异的基因座。对D-丝氨酸脱氨酶基因(DsdCXA)周围区域的持续研究尤其引人注目。编码D-丝氨酸脱氨酶的dsdA的等位基因敲除突变体在1型菌毛介导的黏附表达上没有改变，但在感染UTI上升模型的小鼠的膀胱或肾脏定植方面比野生株强300倍。DsdDC是dsdXA转录的正效应因子，也是lysR家族的一员。通过体内和体外基因表达技术，我们将检验D-丝氨酸通过与双链DC或其他共效应物相互作用影响多个基因表达的假设，这些基因直接影响小鼠疾病模型中CFT073的发病机制。我们还将确定环境条件和其他影响dsdCXA基因表达的基因。两个这样的候选基因是ipuAB(泌尿系病原体的整合酶样蛋白)，它们与CFT073染色体上的dsdCXA基因以及其他泌尿系致病大肠杆菌的dsdCXA基因紧邻。IpuAB是1型菌毛相开关重组酶FIMB和FIME的同源物，它们与大肠杆菌1型菌毛FIM操纵子连锁并控制其表达。我们将检验这样一种假设，即这些基因提供了一个额外的相位切换系统，控制dsdCXA或其他未知基因的表达。这项拟议项目的目标是识别和表征与人类严重疾病有关的大肠杆菌的关键毒力基因。这些信息将有助于开发新的化疗和疫苗策略。

DESCRIPTION (provided by applicant): Escherichia coli is the most common cause of community acquired urinary tract infection (UTI) and a leading cause of nosocomial UTIs and sepsis. There are an estimated 8 million physician visits per year in the U.S for UTIs with significant associated morbidity and expense (> $1,000,000,000). We tested the hypothesis that virulence genes responsible for the pathogenesis of life-threatening E. coli extraintestinal infections, such as pyelonephritis and sepsis can be identified by comparison of the genome sequence of urosepsis E. coli strain CFT073 to either E. coli laboratory strain MG1655 or O157:H7 strain EDL933. We identified >300 CFT073-specific loci. The continued study of the region surrounding the D-serine deaminase genes (dsdCXA) is especially compelling. An allelic knockout mutant of dsdA, that encodes D-serine deaminase, is unaltered in expression of type 1 pili-mediated adherence, but 300-fold more competitive than the wild type strain in colonizing the bladder or kidney of mice infected in an ascending model of UTI. DsdC is a positive effector of dsdXA transcription and a member of the lysR-family of regulators. By in vivo and in vitro gene expression techniques we will test the hypotheses that D-serine through interaction with either dsdC or other co-effectors affects expression of multiple genes that directly influence CFT073 pathogenesis in murine models of disease. We will also identify environmental conditions and additional genes that affect the expression of the dsdCXA genes. Two such gene candidates are ipuAB (integrase-like proteins of uropathogens) that are immediately adjacent to the dsdCXA genes in the chromosome of CFT073 as well as other uropathogenic E. coli. ipuAB are homologs of the type 1 pili phase-switch recombinases, fimB and fimE that are linked to and control expression of the E. coli type 1 pilus fim operon. We will test the hypothesis that these genes provide an additional phase-switch system that controls expression of dsdCXA or other unknown genes. The objective of the proposed project is to identify and characterize critical virulence genes for E. coli involved in serious human diseases. This information will be of use for the development of new chemotherapeutic and vaccine strategies.