肺炎克雷伯菌肝脓肿并发脓毒血症及迁徙性感染细菌毒力机制研究

Klebsiella pneumoniae has now been the dominant pathogen although the Escherichia coli was the most common pathogen for community acquired liver abscess. However, Klebsiella pneumoniae liver abscess is highly prone to be concomitant with sepsis and metastatic infection compared to Escherichia coli liver abscess. This Klebsiella pneumoniae is defined as hypervirulent Klebsiella pneumoniae (hvKP) because its distinctive characteristics in contrast to classic Klebsiella pneumoniae (cKP). The capsular polysaccharides and mucoviscosity-associated gene A (magA) are believed to be associated with the phenomenon of metastatic infection for patients with Klebsiella pneumoniae liver abscess, however, the exact underlying mechanisms have not been elucidated yet. We have completed the data analysis of 280 patients with community acquired liver abscesses, of which, Klebsiella pneumoniae liver abscess accounted for 78.9% and 37 cases were accompanied with metastatic infection. Moreover, 45 Klebsiella pneumoniae strains isolated from liver abscess and another 12 strains isolated from the metastatic infection for patients with Klebsiella pneumoniae liver abscess have been collected in our lab. Meanwhile, clinical cases with community acquired liver abscess and more isolates will continually be collected. In this proposal, the differences of infection ability and virulence genes would be compared within various strains with the infection mice model, in vivo imaging system and comparative genomics technologies. Thus, the discovery of underlying virulence mechanisms associated with the high prevalence of concomitant sepsis and metastatic infection in patients with Klebsiella pneumoniae liver abscess will be the basis for the improvement of patients’ outcomes and further development of therapeutic monoclonal antibody.

近年来肺炎克雷伯菌已取代大肠埃希菌成为社区获得性肝脓肿最重要的致病菌，肺炎克雷伯菌肝脓肿极易并发脓毒血症及迁徙性感染并严重影响患者预后。由于其所致感染的临床特征与传统的肺炎克雷伯菌(cKP)不同，被称为“高毒力肺炎克雷伯菌(hvKP)”。现有研究认为其高毒力主要与致病毒力相关因子荚膜多糖及粘性相关基因(magA)等相关，但仍不能很好解释其致病机制。本课题组已完成280例社区获得性肝脓肿临床资料分析，发现肺炎克雷伯菌肝脓肿占78.9%，其中37例发生了迁徙性感染，并已保留肝脓肿病原菌45株及迁徙性病灶分离菌株12株。本课题将在继续收集临床病例及分离菌的基础上，采用动物感染模型、活体动物成像、比较基因组学等技术，从感染能力、毒力基因等方面阐明肺炎克雷伯菌肝脓肿易致脓毒血症和迁徙性感染的机制，为改善临床预后及单克隆治疗抗体的开发提供基础。

近年来肺炎克雷伯菌已取代大肠埃希菌成为社区获得性肝脓肿最重要的致病菌。这种肺炎克雷伯菌肝脓肿（K. pneumoniae induced pyogenic liver abscess, KP-PLA）极易并发脓毒血症及迁徙性感染并严重影响患者预后，被称为“高毒力肺炎克雷伯菌(hvKP)”。但其主要毒力因子及致病机制尚不明确。本研究拟通过比较基因组学、基因敲除和回补，结合细胞和动物模型研究，阐明KP-PLA易出现迁徙性感染及脓毒血症的机制，揭示相关毒力基因。.研究通过比较临床296例KP-PLA或其他病原菌肝脓肿发现，KP-PLA多合并糖尿病基础（49.7% vs. 36.4%, P = 0.027），且更易发生远处转移（10.6% vs. 3.7%, p = 0.038）。研究发现，hvKP菌株在小牛血清中生长明显快于经典型肺炎克雷伯菌（ckP），而对人血清杀伤的抵抗能力强于cKP，hvKP较cKP存在明显的生存优势。. 45株肝脓肿分离肺炎克雷伯菌中26株（57.8%）MLST表型为ST23型，K1血清型占大多数，有31（68.9%）株，其次为K2血清型，有9株。毒力基因分析表明，45株细菌中，31株细菌（68.9%）为magA阳性，所有细菌均为rmpA阳性。而只有13株细菌拉丝实验为阳性，占28.9%。说明ST实验判断是否高毒力不可靠。. 比较基因组学显示71株hvKP菌株中除magA, rmpA, uge, allS等基因分布比例显著高于41株cKP外，hvKP菌株中铁转运相关基因Kfu, iroN, iutA携带率显著增高（均P<0.05）。这些铁转运相关基因很可能与KP-PLA易出现迁徙性感染及脓毒血症的机制相关，为改善临床预后及单克隆治疗抗体的开发提供基础。. 本项目研究期间，协助培养博士研究生3名。发表相关论文5篇，其中SCI4篇。