牦牛源鲍氏志贺菌的鉴定及对BALB/c小鼠的致病性

Identification of Shigella boydii in Yak and Its Pathogenicity to BALB/c Mice

本试验旨在对从待屠宰健康牦牛中分离的志贺菌进行鉴定及确定分离株的致病性。通过形态染色、培养特性、生化特性、血清型鉴定、16SrRNA基因序列分析以及BALB/c小鼠的LD50测定等方面对分离株进行系统鉴定,并对分离株进行电镜观察和药敏试验。结果显示,分离株形态染色、培养和生化特性符合志贺菌的特点,血清型鉴定为鲍氏6型志贺菌,16SrRNA基因序列系统演化分析表明,分离菌株与人源鲍氏志贺菌和宋内志贺菌亲缘关系近,而与其他动物志贺菌亲缘关系较远,分离株对BALB/c小鼠具有致病性,其LD50值为2.5×107.5 CFU,药敏试验结果显示分离菌株对常用抗生素无耐药性。本次试验首次从健康牦牛中分离的鲍氏6型志贺菌具有较强的致病性,与人源菌株亲缘关系较近,提示牦牛中分离的鲍氏志贺菌具有公共卫生学意义。

The aim of this study is to identify Shigella isolated from healthy slaughter yak, and to determine its pathogenicity to mice. The isolate was identified and eventually characterized by using several methods, including morphology observation, culture characteristics, biochemical tests, serotyping, 16S rRNA sequencing, electron microscopy and evaluation of pathogenicity to BALB/c mice. The results showed that morphological, culture and biochemical characteristics of the isolate is consistent with that of Shigella. The isolate was serotyped as Shigella boydii type 6. Phylogeny analysis based on 16S rRNA indicated that the isolate has close relationship with Shigella boydii and Shigella sonnei in human, and has further relationship with the Shigella from other animals. The isolate is pathogenic to BALB/c mice, and the LD50 is 2.5 ×107.5CFU. The bacterium is not resistant to antibiotics commonly used. We isolated Shigella boydii type 6 from yak for the first time. The isolate is highly pathogenic and phylogentically related to human Shigella, indicating important significance of yak Shigella in public health.