Bolotin Shelly, Fuller Jeffrey D, Bast Darrin J, de Azavedo Joyce C S
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
FEMS Immunol Med Microbiol. 2007 Dec;51(3):547-54. doi: 10.1111/j.1574-695X.2007.00334.x.
Streptococcus iniae causes invasive disease and death in fish, and to a lesser extent, sporadic cases of soft-tissue infections in humans. A two-component system termed sivS/R, which regulates capsule expression, was previously identified and characterized. In this study, it is shown that a sivS/R deletion-insertion mutant, termed 9117Deltasiv, causes transient bacteremia and reduced virulence compared with the parent strain when tested in a murine model of bacteremic infection. Furthermore, real-time PCR studies indicated that SivS/R regulates the expression levels of the streptolysin S structural gene, sagA, as well as the CAMP factor gene, cfi. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of S. iniae spheroplasts revealed downregulation of three surface proteins in the mutant strain compared with the parent strain. These proteins were identified by MS to be a putative lipoprotein, a hyaluronate-associated protein and a pyruvate kinase. This study demonstrates that SivS/R regulates virulence in vivo, and controls the expression of a number of genes in S. iniae.
海豚链球菌可导致鱼类发生侵袭性疾病和死亡，在较小程度上，还会引发人类散发性软组织感染病例。先前已鉴定并表征了一种名为sivS/R的双组分系统，该系统可调节荚膜表达。在本研究中，结果表明，与亲本菌株相比，一种名为9117Deltasiv的sivS/R缺失插入突变体在菌血症感染小鼠模型中进行测试时，会导致短暂菌血症且毒力降低。此外，实时PCR研究表明，SivS/R可调节链球菌溶血素S结构基因sagA以及CAMP因子基因cfi的表达水平。与亲本菌株相比，海豚链球菌原生质体的十二烷基硫酸钠聚丙烯酰胺凝胶电泳显示突变菌株中三种表面蛋白的表达下调。通过质谱鉴定，这些蛋白为一种假定的脂蛋白、一种透明质酸相关蛋白和一种丙酮酸激酶。本研究表明，SivS/R在体内调节毒力，并控制海豚链球菌中一些基因的表达。
