D-serine/DsdCXA Control of E. coli Uropathogenesis

描述（由申请人提供）：大肠杆菌是社区获得性尿路感染（UTI）的最常见原因，也是院内尿路感染和败血症的主要原因。据估计，美国每年有800万名医生因尿路感染就诊，其发病率和费用都很高（10亿美元）。我们验证了这样一个假设，即通过比较尿脓毒症大肠杆菌菌株CFT073与大肠杆菌实验室菌株MG1655或O157:H7菌株EDL933的基因组序列，可以鉴定出导致危及生命的大肠杆菌肠外感染（如肾盂肾炎和脓毒症）发病的毒力基因。我们鉴定出了300个cft073特异性位点。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等位基因敲除突变体在1型毛介导的粘附性表达中没有改变，但在感染尿路感染的上升模型小鼠的膀胱或肾脏中定植比野生型菌株更具300倍的竞争力。DsdC是dsdXA转录的正效应因子，是lysr调节家族的成员。通过体内和体外基因表达技术，我们将验证d -丝氨酸通过与dsdC或其他协同效应物的相互作用影响直接影响CFT073发病机制的多种基因表达的假设。我们还将确定影响dsdCXA基因表达的环境条件和其他基因。两个这样的候选基因是ipuAB（尿路病原体整合酶样蛋白），它紧邻CFT073和其他尿路致病性大肠杆菌染色体上的dsdCXA基因。ipuAB是连接并控制大肠杆菌1型菌毛膜操纵子表达的1型菌毛开关重组酶、fimB和time的同源物。我们将测试这些基因提供控制dsdCXA或其他未知基因表达的额外开关系统的假设。拟议项目的目的是鉴定和表征大肠杆菌涉及严重人类疾病的关键毒力基因。这一信息将用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.