STUDIES ON PREVENTION OF VIBRIO VULNIFICUS SEPTICEMIA

1.创伤弧菌引起的败血症的特点是继发性皮肤水肿损伤的形成。为了阐明这一过程，本文对引起皮肤损伤的主要毒素金属蛋白酶（VVP）的作用机制进行了研究。研究发现，VVP通过n端催化结构域与膜受体的直接结合，诱发肥大细胞的胞外组胺释放，并通过酶原有限的蛋白水解和活性酶（激活因子XII和血浆钾激肽）的生成，激活缓激肽生成级联反应。创伤可以感知细胞密度，调节各种毒素编码基因的表达，以及VVP。这种协调调节系统被称为群体感应（QS）系统。本研究表明，创伤弧菌分泌一种类似信息素的小物质作为信号分子，当该信号分子分泌达到一定的临界值时，细菌启动QS…More系统，在表达水平上刺激VVP的产生。虽然在37℃下也有效，但QS系统在较低的温度下更有效，这表明创伤弧菌可以在间隙产生更多的VVP，而不是在肠道或血液中产生。细胞毒性溶血素（VVH）是创伤弧菌产生的另一种毒素。由于这种毒素是如此独特，编码VVH的vvhA的存在已被记录为该物种分类的可靠证据。从鳗致病性菌株CDC B3547中分离出的VVH与人致病性菌株表现出明显不同的特性，因为其c端结构域有3个氨基酸残基被取代。测定了CDC B3547病毒vha的核苷酸序列，设计了该基因特异性PCR引物。用引物进行基因检测，结果表明引物可用于鳝致病性菌株的特异性选择。因此，所设计的PCR引物可用于创伤弧菌的基因分型。少

1.The septicemia caused by Vibrio vulnificus is characterized by formation of the secondary edematous skin damage. In order to clarify the process, action mechanisms of the metalloprotease (VVP), a major toxin causing the skin damage, was studied. It was found that VVP evoked the exocytotic histamine release from mast cells via direct binding of the N-terminal catalytic domain to the membrane receptor, and that it activated the bradykinin-generating cascade through limited proteolysis and generation of the active enzymes, activated factor XII and plasma kallikrein, from the zymogens.2.V.vulnificus can sense the cell density and regulate expression of various genes encoding toxins, as well as VVP. This coordinated regulation system is called the quorum-sensing (QS) system. The present study showed that V.vulnificus secreted a small pheromone-like substance as a signal molecule, and that when the signal molecule secreted reached to a crucial threshold level, the bacterium operated the QS … More system and stimulated VVP production at the expression level. Although it was also effective at 37 C, the QS system functioned more effectively at lower temperature suggesting V.vulnificus can produce more VVP at the interstitial space but not in the intestinal tract or blood stream.3.The cytotoxic hemolysin (VVH) is another toxin produced by V.vulnificus. Since this toxin is so unique, the presence of vvhA encoding VVH has been documented to be a reliable evidence for classification to this species. VVH from an eel-pathogenic strain, CDC B3547, showed significantly different properties to that from human-pathogenic strains because three amino acid residues in the C-terminal domain are substituted. The nucleotide sequence of vvhA of CDC B3547 was determined, and the PCR primers specific to the gene was designed. The genetic test using the primers indicated that they were useful for specific selection of eel-pathogenic strains. Therefore, the PCR primers designed might be suitable for genotyping of V.vulnificus strains. Less