| Summary: | 碩士 === 國立成功大學 === 生物科技研究所碩博士班 === 90 === Klebsiella pneumoniae is the common pathogen of nosocomial and community-acquired infections. K.p. usually causes systemic infection and the high mortality even if antibiotic treated. The incidence of K.p. pyogenic liver abscess was higher and higher recently, there even was 82.1% in Taiwan. In addition, extrahepatic metastases, such as septic endophthalmitis, are often occurred with serious complications. The high mortality rate and high incidence of K.p. pyogenic liver abscess in Taiwan make further investigation is necessary.
The current research had been evidenced that capsules and lipopolysaccharide were the virulence factor of K.p.. The other virulence factors are currently being studied. The exact mechanism of increasing incidence of K.p. liver abscess in Taiwan is unclear, so we want to look for other proteins involved in the pathogenesis of K.p. from its genomic library.
dnase1 (D1) and dnase2 (D2) cloned from two strain K.p. had different LD50 value, K.p.w.t. (LD50= 106) and K.p.129 (LD50<102) genebank. In the research on genetic conservation, D1 can be amplified by PCR in clinical K.p. isolated from patients with urinary tract; D2 gene detected in K.p. isolated from patient, the ratio of death is high. To investigate the correlation of D2 with respect to the virulence of K. p., we constructed and expressed the D2 protein, and observated the protection effect of active immunization and passive immunization in animal model. These results of protect effect was 60% in active immunization and 40% in passive immunization.
In order to study the virulence roles of dnase2 in the clinical infection of K.p., several isogenic dnase2-deficient strains were constructed by using integrated plasmid to disrupt the orginal dnase2 gene. The 50% lethal does of isogenic dnase2-deficient was equal to wild type (K.p.129). According to the localized experiment, D2 protein located in periplasm region of K.p.129. We supposed dnase2 may not be a very important virulence factor of K.p.129, it maybe help K.p.129 to attack host during infection process.
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