salmonicida are based on findings with media generally used in isolation 

 and cultivation of that organism (agar., gelatin, milk, etc.)' From a 

 study of 120 strains of the organism they found general uniformity 

 except for variations in; (1) gas production from glucose and mannite^ 

 (2) rapidity of liquefaction of gelatin and coagulated serumj and (3) 

 rate and degree of pigment production. 



Stevens and Keil (1931) isolated an atypical organism during an 

 epidemic of furunculosis which they claimed later reverted to the 

 typical B. salmonicida . That this was a true variant of B. salmonicida 

 was disputed ty Davis in a discussion of their paper during the annual 

 meeting of the American Fisheries Society (1931). He did not doubt 

 that they were dealing with true furunculosis, but he did feel that at 

 the beginning of the epizootic, the symptoms did not fit the disease, 

 and that the organism they isolated at that time did not represent a 

 variant but a secondary infection. In spite of Davis' objections, it 

 might be wise to relate the findings of these workers. 



The organism of Stevens and Keil (1931) "was obtained in pure 

 culture from heart-blood and liver. It measured from 5 to 8 ;i in length 

 and from 0.8 to 1.1 ;i in width. The ends were rounded and there was a 

 tendency in many to taper slightly towards both ends. It was non-motile 

 and Gram-negative. In the exact center of many of the organisms was a 

 very pronounced unstained oval area that had every appearance of being a 

 spore, and was so regarded by a number of observers who examined direct 

 smears from heart blood and fluid of unbroken muscular lesions. Such 

 organisms survived incubation at 37° C. but were killed at 57° C. In 

 older cultures and upon transplanting the morphological appearances were 

 changed and many shorter, typical furunculosis bacteria were present 

 together 7»ith longer forms showing pair formation and bipolar staining 

 (often noted in typical B. salmonicida ). In all later transplants the 

 organism had apparently reverted to forms usually encountered in 

 investigations of furunculosis. 



Dissociation— the formation of S, R, and G colonies 



Duff (1937) has been the sole worker to date on this aspect of 

 the stucfy of Bo salm onicida . He used a strain of B. salmonicida 

 possessing the characters of a recently isolated sample. He subcultured 

 the organism every 48 hours at temperatures between 19° C. and 21° C. in 

 phenol broth and lithium chloride. 



Dissociation in Phenol Broth Series (Duff 1937) 



Duff (1937) found that three abnormal colony types arose out of 

 the passage of the organism through phenol broth. From two serial tubes 

 when plated on nutrient agar came giant colonies (5 to 8 mm. in diameter 

 in 96 hours) in place of normal colonies (about 2 mm.). Typical brown 



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