Studies on the mechanisms to expose virulence by a combined effort of capsule-positive and -negative Streptococcus suis

2015 Fiscal Year Final Research Report

• Project/Area Number: 26660226
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Veterinary medical science
• Research Institution: The University of Tokyo
• Principal Investigator: Sekizaki Tsutomu 東京大学, 農学生命科学研究科, 教授 (70355163)
• Co-Investigator(Renkei-kenkyūsha): OSAKI MAKOTO 国立研究開発法人農業・食品産業技術総合研究機構, 動物衛生研究所, 主任研究員 (80355164) ; TAKAMATSU DAISUKE 国立研究開発法人農業・食品産業技術総合研究機構, 動物衛生研究所, 主任研究員 (60414728) ; OKURA MASATOSHI 国立研究開発法人農業・食品産業技術総合研究機構, 動物衛生研究所, 主任研究員 (60508315)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: 豚レンサ球菌 / 莢膜 / 心内膜炎 / 病原因子 / 遺伝子変異

Outline of Final Research Achievements

Streptococcus suis was solely isolated from 59 out of 70 porcine endocarditis samples. Both of encapsulated and unencapsulated S. suis were found in the 26 samples, indicating coexistence of two phenotypes. Pairs of an encapsulated and an unencapsulated isolates were selected from each sample. The isolates in the same pair belonged to the same sequence type by MLST analysis. Whole genome sequencing showed that all the unencapsulated isolates had nonsynonymous mutations in the capsule polysaccharide synthesis (cps) genes. Genome-wide comparison of the isolates showed that the isolates in the same pair were the most closely resembled, and those originated from the same farm were more similar than those from different farms. In a few pairs, encapsulated isolates from the same farm were more similar than those of unencapsulated. These results suggest that the mutation in the cps genes occurred independently in different farms and some pairs occasionally persist to occur the next infection.

Free Research Field

獣医細菌学