STREPTOCOCCUS PYOGENES 349 



work by Andrewes and Horder and by Buerger l confirms the irregu- 

 larity of the fermentation reactions within this group. 



Andrewes and Horder suggest the following classification: 



(1) Streptococcus pyogenes. Grows in long chains and ferments lactose, 

 saccharose, and salicin; does not coagulate milk. Streptococci which cause 

 suppurative lesions or severe systemic infections belong to this group. 



(2) Streptococcus mitis. A saprophytic type found frequently in the mouth 

 which shows the same cultural characteristics as the streptococcus pyogenes, 

 but grows in short chains. 



(3) Streptococcus anginosus. Found frequently in throats of scarlet-fever 

 patients which differs from the pyogenes only in coagulating milk. 



(4) Streptococcus salivarius. A short-chain type which ferments lactose, 

 saccharose, and raffinose, and coagulates milk. Streptococci of this type are 

 found frequently hi the mouth, but are rarely pathogenic. 



(5) Streptococcus fecalis. A short-chain type which ferments lactose, sac- 

 charose, and mannite. This type is found normally in the intestine, and is 

 occasionally pathogenic. 



(6) Streptococcus equinus. A short-chain type which does not ferment lac- 

 tose. Found in horse dung and never pathogenic. 



Quantitative determinations of the amount of acid formed in vari- 

 ous sugars by different races have also been made by Winslow and 

 Palmer 2 and others, but have led to no satisfactory classification. 



Studies by Hopkins and Lang seem to show that the streptococci 

 found in most human infections may be differentiated from the ordinary 

 saprophytic types by the fact that they ferment lactose and salicin, 

 but fail to ferment raffinose, inulin, or mannite. According to their re- 

 sults, the usual saprophytic types found in the mouth either fail to fer- 

 ment salicin or ferment raffinose or inulin, whereas the usual fecal types 

 ferment mannite. They also found in infection mannite fermenters 

 which were apparently of fecal origin. Streptococci which gave the 

 same fermentative reaction as the mouth saprophytes were, however, 

 frequently found in malignant endocarditis. 



Probably the most reliable method of determining the interrelation- 

 ships existing between bacteria, not only within this group, but in all 

 bacterial classes, is that depending upon their reactions to immune 

 sera. The work of Aronson, 3 Marmorek, 4 and others has shown that 

 streptococcus immune sera produced with any one race of pyogenic 



1 Andrewes and Horder, Lancet, 1906; Buerger, Jour. Exp. Med., ix, 1907. 



2 Jour, of Inf. Dis., No. viii, 1910, 1. 



3 Aronson, Berl. klin. Woch., 1902; ibid., 1903. 4 Marmorek, Berl. klin. Woch., 1902. 



