Analysis of protective antigen and virulence factors of Lactococcus garvieae, fish bacterial pathogen

摘要：对加维氏乳球菌进行了细胞表面结构的检测。发现了两种细胞被膜菌株：高度发达的被膜(KG9408)和微被膜(MS93003)，它们携带菌毛状成分，从细胞表面伸出。一株(NSS9319)的细胞表面既没有细胞膜，也没有菌毛状结构。高度发达的细胞壳菌株对鱼类的毒力高于微囊株和非囊株。KG9408株与MS93003株和NSS9310株对这3株噬菌体的敏感性有明显区别。用福尔马林灭活乳杆菌KG9408和MS93003免疫黄尾鱼，诱导出对乳球菌感染的免疫保护。但NSS9310免疫后也产生了免疫保护作用，保护水平显著低于KG9408和MS93003。NSS9310的免疫诱导产生保护作用。用KG9408和MS93003黄尾免疫血清被动免疫，对黄尾金龟子有较强的保护作用，感染后细菌清除迅速。用兔抗KG9408和MS93003兔抗血清和黄尾抗KG9408和MS93003血清免疫印迹分析表明，NSS9310没有检测到与KG9408和MS93003菌株相同的条带。

ABSTRACT : Strains of Lactococcus garvieae were examined for the presence of cell surface structures. Two types of cell capsular strains such as highly developed capsule (KG9408) and micro-capsule (MS93003) of L. garvieae were found, carrying fimbrie-like components, projecting from cell surface. While one stain (NSS9319) has neither cell capsular nor fimbrie-like structures on its cell surface. Highly developed cell capsular strain indicated higher virulence to fish than that of micro-capsular or non-capsular strain. Bacteriphage susceptibilities to these three strains were clearly distinguished from KG9408 to MS93003 and NSS9310 strains. Immune protection against Lactococcus garvieae infection was induced in yellowtail, Seriola guinqueradiata immunized with formalin-killed L. garvieae KG9408 and MS93003. However immune protection was also induced by immunization of NSS9310, the level of protection was significantly lower than that of KG9408 andMS93003. protection was induced by immunization of NSS9310. Passive immunization with yellowtail immune sera raised against KG9408 and MS93003 conferred strong protection to yellowtail with the rapid bacterial clearance after the infection of L. garvieae. Immunoblotting analysis of proteins extracted from L. garvieae strains using rabbit anti-KG9408 and MS93003 serum, and yellowtail anti-KG9408 and MS93003 serum indicated that some bands from NSS9310 were not detected as seen in KG9408 and MS93003 strains.