Sniaszko and Friddle (19/+9b) isolated a new bacterium from an 

 outbreak of ulcer disease among brook trout. This organism was a (Sram- 

 negative rod, nonmotile, facultatively anaerobic, but groTdng better 

 aerobically. It did not liquefy gelatin nor produce changes on litmus 

 milk but fermented some sugars with the production of acid but no gas. 

 It could be propagated only on media containing fresh blood or on 

 sterilized (by filtration) trout tissue extracts. 



In several experiments, brook, broiTO, and rainbow trout 

 fingerlings were inoculated by parenteral injection of pure cultures 

 of this newly isolated bacterium. In all cases, infection occurred with 

 heavy mortality. Since all the brown and brook trout used in the 

 experiments originated from lots having a history of furunculosis, the 

 new bacterium was often accompanied by B. salmonicida . From inoculated 

 rainbow trout, originally free from furunculosis, the new bacterium was 

 regularly reisolated in pure culture. 



During an outbreak of ulcer disease among yearling brook trout 

 at the Westfield hatchery (Wisconsin), Flakas (1950a) found predominantly 

 a Gram-positive rod with but few B, salmonicida in lesions. The Gram- 

 positive rod gave the following biochemical reactions; The production 

 of acid in maltose, dextrose, and sucrose, but no change in lactose and 

 mannitol; reduction of nitrate broth; no production indol in peptone 

 broth; no liquefaction in gelatin and the production of a slight amount 

 of acidity in milk. The lesions found on the trout were not like those 

 usually found in furunculosis but like those of ulcer disease, i.e., 

 they possessed a white ulcerous center with a periphery of reddened 

 tissue and were localized in the superficial muscle layers. Those lesions 

 found in experimental trout were also unlike furunculosis. 



The exact relationship between these two organisms and ulcer 

 disease is unknoim. Flakas (1950a) suggested that ulcer disease may be 

 the result of the action of a bacterium of low virulence, such as the 

 Gram-positive rod isolated, combined with an arrested form of a usually 

 highly virulent organism such as B. salmonicida . 



Snieszko and associates (1950a) and Snieszko and Friddle (1950) 

 isolated another organism from brook trout with ulcer disease. Tliis 

 organism fitted best into the genus Hemophilus and they named it H. 

 piscium . In lesions the bacteria occurred as discrete rods with rounded 

 ends and measured 0,5 to 0.7 by 2.0 microns (>i). They stained uniformly 

 or bipolarly with Giemsa stain. In 2-day-old cultures grown on agar 

 slants, cells were 0o8 to 1,0 by 1,0 to 3.0 p.; the average dimensions 

 were 0.8 by 2,0 )x. Cells were arranged singly, in pairs or in irregular 

 groups, and occasionally as filaments up to 12 ;n long. In liquid media 

 cells were of the same size and usually arranged in irregular clusters. 

 They were Gram-negative with I-Iucker's modification of the Gram method. 

 They did not form endospores and were nonmotile in hanging-drop 

 preparations and in semisolid agar stabs. Capsules were absent with 



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