Isolation and charactrization of Vibrio vulnificus acapsular mutants

• Main Authors: Yu-Chin Jen, 任佑君
• Other Authors: Lien-I Hor
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/81925529265511125195

碩士 === 國立成功大學 === 微生物及免役學研究所 === 82 === Vibrio vulnificus, a marine bacerium, causes serious wound infection and septicemia with a high mortality rate in persons with underlying diseases that result in immunocompromised conditions and/or high serum iron levels, such as chronic cirrohosis and hemochromatosis. It is important to understand the pathogenesis of this bacterium in order to be able to properly prevent and treat its infectious diseases. Most V. vulnificus are encapsulated. To study the role of the capsular polysaccharide in the pathogenesis of this microorganism, spontaneous or U.V mutagenized translucent (morphology of acapsular strains) mutants were isolated from three clinical isolates and characterized for their virulence in mice and properties relating to pathogenesis. It was shown that the LD50 of acapsular mulants is higher than their parental strains by 3 logs or more, either by intraperitoneal injection or force feeding, in the mice pretreated with iron or CCl4. This result indicates that the capsule is an important virulence factor of V. vulnificus in susceptible hosts. The growth rates of acapsular mutants were similar to their parental strains, in either rich or iron-limitng media. Adherence of the acapsular mutans to an epithelial cell line HEp-2 was less efficient, but the hemagglutination ability was slightly higher than their parental strains indicating that the capsule but not the hemagglutinin(s) is involved in adherence to the epithelial cells. The ability of the acapsular mutants to resist killing by human serum was also reduced in two of the three strains. The third one, although exhibited equal resistance to human serum with its parental strain, was rapidly cleared from the blood of an infected mouse, suggesting that the capsule may protect the bacteria from other host defense mechanisms, such as phagocytosis. In another study, we tried to develop transposon mutagenesis in V. vulnificus. We used two transposon (Tn5 or TnphoA)-containing plasmids to mutagenize this bacterium.