TABLE 46— continued 

 Fermentation Reactions of Salmonella Group (modified from Katjffmann 1941) 



Gas|+ 



r+ 



Arabinose-xylose and! +1 

 organic acids | x 



= normal amount. 

 = small or absent. 



= positive within 3 days. 



= positive usually 4—8 days. 



= late or irregularly positive, often negative. 



= variable with different strains. 



Stern's glycerol 



f++ = lilac in 1-3 days. 



[+ = purple or lilac in 4-8 days. 



Gelatin /+ ^ ^^^^'^ liquefaction. 

 \± = slow liquefaction. 



The second reaction was described by Bitter, Weigmann, and Habs (1926). It is 

 essentially a test of the ability of the organism to grow in a synthetic medium containing 

 ammonium salts as the main source of nitrogen. A 1 per cent, solution of sugar, of which 

 the most generally useful is rhamnose, is added to test the fermentative power of the 

 strain under these conditions. Strains that grow readily ferment the sugar and are 

 referred to as " ammonium-strong." Strains that grow poorly and fail to ferment the 

 sugar are referred to as " ammonium-weak." The result of the test may be negative, 

 not because the organism cannot grow in an ammonium medium, but because, like some 

 strains of Sahn. paratyphi B, it fails to ferment rhamnose. In practice, the inoculated 

 medium is incubated for 20 hours at 37° C. ; methyl red is then added to determine 



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