NON-SPECIFIC PYOGENIC COCCI 205 



Isolation, Morphology, and Culture. This organism may be 

 most easily isolated from milk by plating in litmus-lactose gelatin. 

 The characteristic non-liquefying colonies surrounded by red 

 may be easily recognized. Its morphologic characters differ 

 in no marked degree from Streptococcus pyogenes. Culturally, 

 many strains of this latter organism appear to be identical with 

 Str. lacticus. In fact, the resemblance is so close that there is a 

 good reason to believe that Str. lacticus is a strain of Str. pyogenes 

 which has adapted itself to a saprophytic life. 



Fig. 88. Streptococcus lacticus (Heinemann, in " Journal of Infectious 



Diseases"). 



Physiology. Its physiologic characters differ in no noteworthy 

 degree from the preceding. Acid is produced from dextrose and 

 lactose. According to Heinemann, the dextro acid is produced 

 by this organism and the levo by the B. lactis acrogenes and other 

 members of the intestinal group. 



The heat resistance of Str. lacticus is of particular importance 

 in connection with pasteurization of milk. It has been generally 

 regarded that pasteurization would certainly kill all organisms 

 of this type, and it has been believed that pasteurized milk would 

 contain only the spores of putrefactive bacteria, and if improperly 



