猪链球菌2型分离株对野生斑马鱼的致病性

以野生斑马鱼为模式动物,对6株mrp＋epf＋sly＋猪链球菌2型（SS2）分离株进行致病性比较。斑马鱼经腹腔接种不同稀释度的SS2分离株,连续观察5d,Kaplan-Meier生存曲线分析并统计半数致死量（LD50）。结果显示,6个分离株对斑马鱼的LD50在10^5cfu-10^6cfu之间,临床株与非临床株的毒力差异不显著（P〉0.05）。从攻毒后死亡的鱼腹腔和脑可分离到SS2,并伴有腹腔出血及肝、肠、脑部炎性病变。表明SS2可感染斑马鱼,为进一步研究SS2的体内感染机制及毒力因子功能等奠定了基础。

Pathogenecity of Streptococcus suis type 2 Isolates to Wild Zebrafish

Wild zebrafishes were used as model animals to evaluate pathogenicity of six Streptococcus suis type 2 (SS2) isolates. The fishes were intraperitoneally inoculated with SS2 isolates serially diluted in PBS, and monitored for five days. Kaplan-Meier survival curves and 50% lethal dose (LD50) were then determined. The results indicated that the LD50 of the 6 SS2 isolates was between 105 to 106 CFU, and there were no significant differences between clinical and non-clinical isolates (P>0.05) in terms of LD50 or the time to reach 50% death. SS2-inoculated fishes showed septicemia as well as hepatitis, enteritis and signs of meningitis as revealed by histological examination. SS2 isolates could be recovered from the peritoneal cavities and brains of challenged yet dead fishes as confirmed by specific PCR.These results showed that zebrafish can be used as the animal model for studies of SS2 pathogenesis.