According to Duff and Stewart (1933) in very young agar cultures nearly 

 all cells are coccoid to ovoid, longer forms appearing in cultures 

 after 2h hours. In blood and iBsions of the host. Marsh (I903) found 

 B. salmonicida generally larger and more bacillary than -when growing on 

 artificial media. A capsule has not been demonstrated, 



B. salmonicida is Gram-negative (Ekmnerich and Weibel 1894 and 

 others), tending to stain unevenly (Marsh 1903, Williamson 1928) and 

 often showing bipolar staining (Williamson 1928), Duff and Stewart 1933) • 

 Marsh (1903) found that methylene blue and thionin gave excellent 

 results. 



Viability 



Temperature, light and drying 



The temperature range for growth of B. salmonicida is 5° to 

 30° or 32° C. (Arkwright 1912, Williamson 1928, Duff and Stewart 1933, 

 Furunculosis Committee 1935). ^ some authors the optimum is stated to 

 be between 20° and 22° C. (Marsh I903, Williamson 1928, Furunculosis 

 Committee 1930) but Siraierich and Weibel (1894) and Davis (1946), claim 

 it to be between 10° and 15° C. These differences in findings could be 

 projected upon (a) variations amongst strains, or (b) variations in media 

 used. Arkwright (1912) found that cultures remained alive at 1° C. for 

 at least 4 months, and that at 35° or 36° C. the organism will sometimes 

 reproduce to a slight extent. Generally at 37° C. either no growth occvirs 

 (Emmerich and Weibel 1894) or cultures soon die (Arkwright 1912, Mettam 

 1914, Williamson 1928) but Duff and Stewart (1933) accustomed a strain 

 to give growth and pigment at this temperature. Williamson (1928) and 

 Duncan (1932) found that a broth culture of the organism was killed in 

 one minute at 60© C. Emmerich and Weibel (1894) also found that 60° C. 

 rapidly killed the organism. Plehn (1911) stated that 40° C. was 

 sufficient to kill it. 



According to Duncan (1932) bright daylight kills the organism. 

 Williamson (1928) showed that B. salmonicida died when dried for 6 hours 

 and Duncan (1932) found that on drying a drop of broth culture at room 

 temperature, the organism did not develop after 24 hours' culturing. 



In water 



Various authors have recorded that B. salmonicida is recovered 

 from distilled water from 4 days to 2 weeks. In unsterilized distilled 

 water Williamson (1928 ) recovered the organism up until 4 days and in 

 sterilized distilled water up until 5 days. Duncan (1932) found the 

 organism to be alive at the end of a week in distilled water and Home 

 (1928) gave a figure of 14 days for survival in distilled water. 



