DAO 51:169-177 (2002)  -  doi:10.3354/dao051169

Cell-surface properties of Lactococcus garvieae strains and their immunogenicity in the yellowtail Seriola quinqueradiata

Tsuyoshi Ooyama1, Yusuke Hirokawa2, Takayuki Minami1, Hiroshi Yasuda1, Toshihiro Nakai3, Makoto Endo2, Lila Ruangpan4, Terutoyo Yoshida2,*

1Miyazaki Prefectural Fisheries Experimental Station, Miyazaki Prefecture, Aoshima, Miyazaki 6-16-3, Japan
2Department of Fisheries, Faculty of Agriculture, Miyazaki University, Miyazaki 889-2192, Japan
3Faculty of Applied Biological Science, Hiroshima University, Higashihiroshima 739-8528, Japan
4Samutsakhon Coastal Aquaculture Development Centre Kkkham, Muang, Samutsakhon 74 000, Thailand
*Corresponding author. E-mail:

Abstract: The cell-surface properties of strains of Lactococcus garvieae were examined. Two capsular types were found, one with a highly developed capsule (KG9408) and one with a micro-capsule (MS93003) carrying fimbriae-like components projecting from the cell surface. One strain (NSS9310) had neither cell capsular nor fimbriae-like structures on its cell surface. The strains with the highly developed capsule were more virulent to fish than either the micro-capsular or non-capsular strains. The KG9408, MS93003 and NSS9310 strains could be clearly differentiated by their susceptibility to bacteriophages. Protection against L. garvieae infection was induced in the yellowtail Seriola quinqueradiata by immunization with formalin-killed L. garvieae KG9408 and MS93003 cells. Although protection was also induced by immunization with NSS9310, the level of protection was significantly lower than that with KG9408 and MS93003 vaccines. Passive immunization with yellowtail immune sera raised against KG9408 and MS93003 conferred strong protection on yellowtail with rapid bacterial clearance after challenge with L. garvieae. Immunoblotting analysis of protein antigens extracted from L. garvieae strains using rabbit anti-KG9408 and anti-MS93003 sera and yellowtail anti KG9408 and anti-MS93003 sera indicated that some bands in KG9408 and MS93003 strains were not detectable in NSS9310.

KEY WORDS: Immunogenicity · Lactococcus garvieae · Seriola quinqueradiata · Cell capsule · Fimbriae

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