Studies on Biotyping, Genotyping of Lactococcus garvieae and Their Effect on Grey Mullet ( Mugil cephalus L. ) Immune System

• Main Authors: Ming-Ann Tsai, 蔡明安
• Other Authors: Shih-Chu Chen
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/73361914248920342219

碩士 === 國立屏東科技大學 === 獸醫學系 === 93 === Lactococcus garvieae is a zoonotic pathogen and rare pathogen with a low virulence in human infection. In Taiwan, it causes infection grey mullet and giant freshwater prawn during summer. Gross pathological showed clouding of cornea, splenomegaly and external haemorrhage. Histopathologically, they showed meningoencephalitis. Physiological and biochemical characteristics of all L. garvieae strains were Gram positive cocci. Almost strains were able to grow at high temperature and media in high salt and pH 9.6. The capsular type of L. garvieae were examined by capsule stain. Capsular phenotype were found in all strains isolated from grey mullet and non-capsular phenotype were found only in one strain isolated from giant freshwater prawn in Taiwan. The phenotypic and genetic analysis results were present for by rapid ID 32 STREP and pulsed field gel eletrophrosis ( PFGE ), respectively. There was 9 phenotypes in L. garvieae isolated from grey mullet and 11 phenotypes in Taiwan. However, L. garvieae from grey mullet exhibited one genotype only and L. garvieae in Taiwan exhibited six genotypes. The formalin-killed whole cell vaccines of L. garvieae III were prepared. Grey mullet were inoculated intraperitioneally with formalin-killed whole cell vaccine from five strains of L. garvieae and followed by a secondary IP injection after primary immunization. Increased nitro blue tetrazolium activity were observed in 3 strains at 2 weeks after primary immunization. However, decreased lysozyme activity were observed in 3 strains at 2 weeks after primary immunization. Peaked antibody titer in the serum of grey mullet were observed at week 6 and 8 after primary immunization and agglutinating titer of 256 in grey mullet were observed. On the cross reactivity, all antisera were not agglutinated capsulated Japanese isolate except it’s homologous bacteria.