克雷白氏肺炎桿菌生物膜與致病機轉之研究:探討pgaC基因扮演的角色

克雷白氏肺炎桿菌（Klebsiella pneumoniae）造成廣泛的社區型或是院內感染，在台灣地區K. pneumoniae 的感染好發於糖尿病患者，易併發多種臨床症狀，如原發性肺炎，化膿性肝膿瘍，腦膜炎，及轉移性眼內炎。生物膜的形成在細菌的抗藥性與致病力上扮演重要角色。我們相信形成生物膜能夠幫助K. pneumoniae適應逆境挑戰。 Poly-N-acetylglucosamine (PGA) 是大腸桿菌生物膜基質中一個必需的組成。利用生物資訊的方法，我們在K. pneumoniae的染色體上找到與大腸桿菌相似的pgaABCD 的基因組。為了探討PGA在K. pneumoniae生物膜生成與致病力上扮演的角色，我們運用同源重組技術將pgaABCD當中負責轉譯glycosyltransferase的pgaC基因剔除。結果發現，pgaC缺失的菌株 (簡稱為pgaC) 在一般培養條件下產生的生物膜與野生型相似，但在添加0.7 M NaCl與0.4% casamino acids的培養液中，pgaC形成的生物膜，其成熟度較野生型的差。萃取胞外與莢膜多醣進行ESI-MS分析發現，pgaC缺失會改變K. pneumoniae的醣類表現，這樣的改變也可以在進行黏性分析時發現，pgaC的菌落黏性在常溫下較野生型的強。然而，菌落的黏性顯然跟致病力間沒有完全的正相關性，因為在小鼠感染的模式中發現，K. pneumoniae散布至腸外器官造成系統性感染的能力在pgaC缺乏後顯著減弱。以上結果顯示PGA在K. pneumoniae的生物膜生成上扮演了一個較為次要的角色，但在細菌毒性與致病力方面卻是必要的。然而對於pgaC如何影響K. pneumoniae醣類生成與修飾上，詳細的機制以及與致病力與菌落黏性之間的關聯仍然需要投入更多努力。

關鍵字

克雷白氏肺炎桿菌； pgaC基因；生物膜

並列摘要

Klebsiella pneumoniae causes a wide range of community- or hospital-acquired infections. In Taiwan, diabetic patients have an increased susceptibility to K. pneumonia infections combined with several clinical syndromes, including primary pneumonia, pyognic liver abscess meningitis and metastatic endophthalmitis. Biofilm formation plays an important role in bacterial resistance and virulence, we believe that can helps K. pneumonia to adapt the challenge from the environment. Poly-N-acetylglucosamine (PGA) is an essential component of the biofilm matrix in phylogenically diverse bacteria. A pgaABCD locus that encodes proteins for PGA biosynthesis was identified in K. pneumoniae genomes. Production of PGA was undetectable in the K. pneumoniae pgaC deletion mutant, △-pgaC, whereas the ability of △-pgaC to form biofilms in various conditions, except incubation under 0.7M NaCl and 0.4% casamino acids , was show loss maturity than its parental strain . The mass spectrometry result revealed that the composition of extracellular and capsular polysaccharides was significantly changed by the loss of pgaC. Loss of pgaC enhanced the hypermucoviscosity phenotype with changes in the polysaccharide composition.In a mouse model, the ability of K. pneumoniae to disseminate into extra-intestinal organs and to induce a systemic infection was significantly attenuated in △-pgaC. Taken together, this study demonstrates that PGA has a minor role in the biofilm formation of K. pneumoniae but is required for the virulence of this bacterium. However, its still need more effort to find out the association with related regulatory mechanism.

並列關鍵字

Klebsiella pneumoniae ； pgaC gene ； biofilm

參考文獻

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克雷白氏肺炎桿菌生物膜與致病機轉之研究:探討pgaC基因扮演的角色

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