5株鼠伤寒沙门菌基因缺失株的生物学特性比较

Characterization of 5 Salmonella typhimurium deletion mutants

为了探讨crp、cya、sipB、crp/cya、crp/sipB基因缺失株成为鼠伤寒沙门菌减毒候选活疫苗的可能性,对缺失株的生物学特性进行研究。结果显示,缺失株的血清型仍和亲本菌株相同,其中crp、cya、crp/cya、crp/sipB与亲本菌株相比失去了利用麦芽糖、乳糖、山梨醇等碳源的能力,也不能分解H2S、半乳糖和鼠李糖,但仍保留了利用葡萄糖的能力。通过口服方式把5株crp、cya、sipB、crp/cya、crp/sipB基因缺失株接种KM小鼠进行毒力测定和免疫保护性测定,结果它们的半数致死量比野生株的至少高700倍,双基因缺失株的毒力更弱,攻毒后crp、cya、sipB、crp/cya、crp/sipB基因缺失株的免疫保护率分别为90.0%,60.0%,50.0%,60.0%,60.0%。结果表明,crp基因缺失株可作为鼠伤寒沙门菌减毒活疫苗的候选株。

To develop a live attenuated vaccine against Salmonella typhimurium,we constructed single or double deletion mutants with deleting crp,cya,sipB,crp/cya,crp/sipB,and their biological characteristics were evaluated.The results showed that the serotype of those strain was identical to the parent SL1344strain;The growth rate of the mutant was slower than SL1344strain;but the crp,cya,crp/cya,crp/sipB mutants were not able to ferment maltose,lactose,and sorbitol.They also had no ability to decompose H2 S,galactose and rhamnose.Compared with the wild-type strain,all five mutants virulence had an increased LD50（700fold）in a mouse model,of which the double mutants were more attenuated than the single mutants.When the immunized mice were infected with the wild-type strain at 4weeks post-immunization,the protection rates induced by the crp,cya,sipB,crp/cya,crp/sipB mutants were 90.0%,60.0%,50.0%,60.0% and 60.0%,respectively.These results showed that the crp mutant may be a potential live vaccine candidate against S.typhimurium.