Serological differences among Photobacterium damsela subsp. piscicida isolates

Serological differences of Photobacterium damsela subsp. piscicida (= Pasteurella piscicida) isolates were determined using yellowtail (Seriola quinqueradiata) and rabbit. antisera. In Oita, Japan, from June to October, 1995, Ph. damsela piscicida was isolated from net-pen cultured diseased yellowtail and sera were collected from fish cultured in the same net-pen. Antisera against formalin-killed cells of three representative isolates were raised in yellowtail and rabbits. The yellowtail antisera were absorbed with homologous or heterologous isolates and used for the agglutinating antibody absorption test. Crude lipopolysaccharides were extracted from the isolates and analyzed by immunodiffusion with rabbit antisera, As a result, three types or antigenic differences were revealed among the isolates by the agglutinating tests with the sera of naturally infected fish and by the absorption tests using yellowtail antisera. Some common and distinctive antigens of the isolates were found by immunodiffusion analysis with rabbit antisera.