SWINE ERYSIPELAS GROUP 



245 



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istic. Each colony is found to be surrounded by a zone of much- 

 branched threads. They permeate the medium, and are not found 

 upon the surface, as is the case with anthrax and other forms which 

 produce colonies with filamentous edges. 



Gelatin stab cultures develop only below the surface of the 

 medium, showing the micro-aerophilic or semi-anaerobic growth 

 characters of the organism. The mature stab has the appearance 

 of a test-tube brush, streaks and disks of growth radiating from the 

 center. Streak cultures do not develop well upon agar or blood- 

 serum except by growth under anaerobic conditions, preferably 

 by absorption of the oxygen by the 

 alkaline pyrogallate method. Bouillon 

 is clouded and produces a grayish- 

 white sediment. Ordinarily no growth 

 occurs upon potatoes, even under 

 anaerobic conditions. 



Physiology. The B. rhusiopathice 

 grows better anaerobically than aerob- 

 ically. It is unusually resistant for 

 a non-spore-producing form. Desic- 

 cation frequently fails to destroy the 

 organism in several weeks. The 

 thermal death-point is recorded by 

 some authors as low as 52 for fifteen 

 minutes, by others as high as 70. 

 The optimum growth temperature is 

 37, but growth occurs well at room- 

 temperatures. Gelatin is not com- 

 pletely liquefied, but generally softened. 



Pathogenesis. Experimental Evidence. Mice die of septicemia 

 when inoculated with pure cultures. Death occurs usually within 

 four days, frequently within forty-eight hours. Field-mice are 

 immune, as are guinea-pigs, cattle, horses and other equines, 

 dogs, cats, chickens, and geese. Rabbits inoculated subcuta- 

 neously develop an edema and redness at the point of inocula- 

 tion, and this erysipelas-like lesion spreads to other parts of 

 the body and the animal dies. Intravenous injection is quickly 

 fatal through the development of a septicemia. The white rat, 



Fig. 103. Bacillus rhusio- 

 pathice, stab culture in gelatin 

 four days (Frankel and 

 Pfeiffer). 



