rmpA基因和铁载体对肺炎克雷伯菌致病性的影响

Hypermucoviscous phenotype has been known to be an importantly virulence factor in Klebsiella pneumoniae(Kp).it still being investigated that rmpA are positive regulators of capsule polysaccharide (CPS)synthesis by binding to the regulator 5'region of capsule genes, and increase the expression CPS gene and the hypermucoviscous phenotype. also, rmpA have different pathogenic effect with different clinical isolates. But the underlying mechanisms are still unclear. Our previously study indicated that hypermucoviscous phenotype of Klebsiella pneumniae had a higher mortality rate than those by infected by classical Klebsiella pneumoniae; further genetic analysis indicated that all of hypermuviscous Klebsiella pneumoniae co-contains rmpA gene and sidrophore genes such as iucA; qualitative and quantitative analysis of production of siderophores also shown that the strains which lower production siderophores had higher virulence to mice. Preliminary experiments indicated that expression of CPS gene in the iron depletion environment. We hypothesized that there may have directly or indirectly interaction between rmpA gene and siderophres then have had in expression of CPS gene. To improve this hypothesis, we will use the gene knock out strains, animal infection models And gel mobility shift assay ( EMSA ) investigates the relationship between rmpA and siderophores and the functional role of rmpA gene and siderophores in Klebsiella pneumoniae infections. we will reveal the mechanisms of capsular polysaccharide biosynthesis，also to provide new drug targets for prevention and treatment of Klebsiella pneumoniae infection .

高粘性厚荚膜是肺炎克雷伯菌的重要的毒力因子。rmpA(regulator mucoid phenotype)是高粘性厚荚膜调控因子，通过增强荚膜多糖（CPS）基因的表达参与高粘性厚荚膜的形成,针对不同临床分离菌株rmpA的致病作用各不相同，其机制不明。我们的前期结果显示，高粘性厚荚膜Kp菌与高死亡率相关，与传统的Kp菌不同均携带rmpA基因和铁载体基因；定量和定性分析铁载体的产量发现，产铁载体越低的Kp菌致病性越强；预实验中还观察到环境缺铁时CPS表达增强。我们推测铁载体与rmpA基因之间存在相互的调控关系并参与CPS基因的表达。为证明这一假设，我们将采用基因敲除、动物感染实验及凝胶迁移实验（EMSA）等技术分析rmpA和铁载体对Kp菌致病性的作用,研究rmpA和铁载体基因的相互作用，揭示Kp菌高粘性厚荚膜形成机制为Kp菌感染症的防治提供新的思路和抗菌药物的新靶点。

目的: 探讨中国哈尔滨的地区高粘性肺炎克雷伯菌的MLST型别和毒力因子的存在模式, 证实铁载体对肺炎克雷伯菌致病性的影响.方法：用拉丝实验的方法筛选高黏性肺炎克雷伯菌; 采用多位点序列分型的方法分析ST型别；用PCR的方法检测毒力相关基因(c-rmpA，p-rmpA/p-rmpA2，magA，iucA，iroN，ybtS，荚膜血清型)；采用基因敲除技术和动物感染实验检探讨菌株的致病性。.结果：（1）哈尔滨地区引起社区获得性感染症的高黏性肺炎克雷伯菌的主要流行株为K2型的ST65株，且普遍携带染色体和质粒编码的高黏性调控因子（c-rmpA和 p-rmpA/p-rmpA2）、铁载体相关基因（ iucA, iroN以及ybtS）；(2) iucA是铁载体产生的主要因素,与高黏性特性协同影响肺炎克雷伯菌的高毒力水平；（3）未知因素可能参与菌株高黏性特性的形成。