blaKPC-2在高毒力肺炎克雷伯菌中的传播机制研究

Hypervirulent Klebsiella pneumobniae (hvKP), a new virulent variant of classic K. pneumoniae (cKP), which often causes liver abscess, sepsis and metastatic infections, are associated with poor prognosis in patients. In recent years, the dramatic increase of KPC-producing K. pneumoniae has posed tremendous challenge to antibacterial therapy. Our previous study (Antimicrob Agents Chemother. 2015, 60(1):709-11) had reported the isolation of blaKPC-2-carrying hvKP strains from 5 patients, and all of them were died of infectious shock. The transmission mechanism of blaKPC-2 in hvKP which make it a virulent as well as a highly-resistant “Superbug” has not yet been elucidated. In the current study, southern blot will be used to locate the blaKPC-2 gene in hvKP isolates; conjugation, transformation assay, plasmid typing and homology analysis will be performed to characterize the blaKPC-2-carrying plasmids; whole-plasmid sequencing will be conducted to illuminate the genetic environment and the mobile genetic elements involving in the transfer of blaKPC-2. The aim of the project is to uncover the transmission mechanism of blaKPC-2 in hvKP, and to offer strategic methods for the control of blaKPC-2 dissemination in hvKP.

高毒力肺炎克雷伯菌（hvKP）是传统肺炎克雷伯菌的新型强毒力变种，常导致肝脓肿、脓毒血症及迁徙性感染并严重影响患者预后。近年来产KPC酶肺炎克雷伯菌在临床的分离率不断增加，给抗感染治疗带来极大的挑战。本课题组前期研究（Antimicrob Agents Chemother. 2015,60(1):709-11）从5例感染性休克死亡的病人中分离到携带blaKPC-2基因的hvKP菌株。blaKPC-2基因进入hvKP菌株，使之成为既产毒又高耐药的“超级细菌”，其传播机制尚未明确。本研究拟通过southern blot对hvKP中blaKPC-2基因进行定位；通过接合转化实验、质粒分型和同源性分析探究blaKPC-2基因的质粒特征；通过全质粒测序明确blaKPC-2基因环境及介导其转移的可移动元件，揭示blaKPC-2基因在hvKP菌株中的传播机制，为控制该基因在hvKP中的传播提供科学依据。

高毒力肺炎克雷伯菌（hvKP）是传统肺炎克雷伯菌的新型强毒力变种，常导致肝脓肿、脓毒血症及迁徙性感染并严重影响患者预后。近年来产KPC酶肺炎克雷伯菌在临床的分离率不断增加，给抗感染治疗带来极大的挑战。我们在感染性休克的死亡病人中分离到多株碳青霉烯类抗生素耐药的高毒力肺炎克雷伯菌（CR-hvKP），同源性分析和基因组学分析发现rmpA2-类pLVPK毒力质粒存在于所有CR-hvKP菌株，质粒消除实验和毒力试验证实该质粒在hvKP的粘液表型和致病性过程均发挥重要作用，进而提示CR-hvKP菌株可能是ST11型CRKP基础上获得毒力质粒进化而来。这些研究结果不仅证实了ST11型CR-hvKP的高毒力高耐药性和高传播性对人类健康造成极大的威胁，更是揭示了CR-hvKP的进化历程，为有效的临床抗感染治疗和及时的感染防控措施提供重要的理论基础。