100 



Figure l. — Comparative rate of 

 mortality of three lots of 0-age sock- 

 eye salmon raised in net pens at 

 Manchester, Wash. Two of the lots 

 were vaccinated with an intraperi- 

 toneal injection of a heat-killed 

 bacterin prepared from Vibrio anguil- 

 larum 775. 



Ordal 1967). Plates were incubated aerobically at 

 23°C. Presumptive identifications of the bacteria 

 were based on the following tests: gram stain, 

 motility and morphology characteristics under 

 phase contrast microscopy, oxidase test (Kovacs), 

 fermentation or oxidation of glucose, and sen- 

 sitivity to the vibriostatic compound 0/129 (2,4- 

 diamino-6,7-diisopropyl pteridine phosphate). 



Further biochemical characterization included 

 tests in Moeller's media for an alkaline reaction 

 with arginine and for lysine decarboxylase, the 

 production of indole, the production of acetyl- 

 methylcarbinol (Voges-Proskauer test), and the 

 ability to ferment arabinose, glycerol, mannitol, 

 sucrose, and galactose. These tests were selected 

 because they were found to be variable among 

 marine vibrio groups established by deoxyribo- 

 nucleic acid homology characteristics (E. J. Or- 

 dal, University of Washington School of Medicine, 

 Seattle, pers. commun.). In all of these tests addi- 

 tional NaCl (1%) was added. 



Table l. — Selected properties of Vibrio anguillarum 775 and 

 Vibrio sp. 1669. 



Antisera for serological comparisons were pre- 

 pared in both rabbits and coho salmon with 

 heat-killed bacterins of V. anguillarum lib and 

 Vibrio sp. 1669 in Freund's complete adjuvant. 

 Rapid slide agglutination tests with the specific 

 antisera were used for initial differentiation. The 

 microtiter system (Cooke Engineering Co.) was 

 used later to determine agglutinin titers, and 

 immunodiffusion techniques were used to further 

 compare antigenic structure and relatedness. 

 Tests were run with unabsorbed antisera and 

 with anti-Vibrio sp. 1669 sera absorbed with V. 

 anguillarum lib. 



Results and Discussion 



Vibrio sp. 1669 was typical of the marine vibrio 

 group: it was characterized as a gram negative, 

 motile, curved, asporogenous rod that was oxi- 

 dase positive, an anaerogenic fermenter, and sen- 

 sitive to the vibriostatic compound 0/129. A 

 slower rate of growth of Vibrio sp. 1669, in com- 

 parison to V. anguillarum lib, was observed on 

 TSA, as well as variations in certain culture reac- 

 tions (Table 1). 



Coho salmon anti-V. anguillarum lib serum 

 with an agglutinin titer of 512 against the ho- 

 mologous bacterium had a titer of 8 against Vib- 

 rio sp. 1669. Immunodiffusion also revealed dif- 

 ferences between the two vibrios. In Figure 2, the 

 inner precipitin lines demonstrate antigenic 

 cross-reactivity (reaction of identity). An addi- 

 tional antigen unique to V. anguillarum lib is 

 demonstrated by the outer precipitin line which is 

 not present in reactions with Vibrio sp. 1669. 



After all detectable agglutinin activity against 



448 



