THE HEMOLYTIC STREPTOCOCCI : GROUPS B AND C 581 



and inulin are not ; the reactions in lactose and salicin are variable (Brown 1939). It 

 may be noted that a considerable proportion of Group B strains form pigmented cells, 

 usually yellow or red in colour (Orla-Jensen 1919, Plummer 1941). 



The great majority of Group B strains that have been adequately identified have been 

 isolated from cases of mastitis in cattle, in many cases under conditions which have made 

 it almost certain that they were the primary cause of the disease. They have occasionally 

 been isolated from the normal human throat and vagina. They are very rarely 

 pathogenic for man. 



Group B, like Group A, clearly demands a label ; and we feel that it may pro- 

 visionally be accorded specific rank. We follow Klimmer and Haupt, and Minett 

 and his colleagues, in giving it the name Str. agalactice (Kitt 1893) (see Klimmer and 

 Haupt 1930, Minett 19356), in preference to the name Str. mastitidis contagiosce, 

 assigned by Nocard and Mollereau (1887) to streptococci isolated from a similar 

 source. There can, we think, be no doubt that, in defining this species, antigenic 

 structure should take precedence over hsemolysin production as a systematic 

 criterion, and that the specific name should be applied to the non-hsemolytic 

 as well as to the hsemolytic strains. "We should, therefore, describe haemolysin 

 production as being an almost constant character within the species Str. pyogenes, 

 but a variable character within the species Str. agalactice ; whether the non- 

 hsemolytic strains of Str. agalactice should be classed as a distinct variety, the future 

 must decide. 



Group C. 



The strains that faU within this group share a common group-specific polysaccharide 

 antigen. The existence of a number of antigenic types can be demonstrated by agglutina- 

 tion. Of Griffith's original series, Tjrpes 7, 20 and 21 were later found to belong to this 

 group. Five fm-ther types among human strains have been differentiated by Simmons 

 and Keogh (1940), and five among equine strains by Bazeley and Battle (1940). The 

 type-specific antigen appears to be of protein nature. On blood agar the colonies tend 

 to be siuTounded by a rather larger zone of hsemolysis than colonies of Group A, the outer 

 edge of the hsemolytic zone being hazy. Colonies of the typical Str. equi type are large, 

 honey- coloured, and of very viscous consistency ; if closely adjacent, they readily flow 

 together, forming a streak of sticky material. Most, but not aU, strains form a filtrable 

 haemolysin. 



In regard to their other biological and biochemical characters Group C strains display 

 certain significant differences among themselves. They produce in glucose broth a final 

 pH intermediate between that produced by Group A strains on the one hand and by Group 

 B strains on the other ; the range covered by the group as a whole appears to vary between 

 pH 4-5 and pH 5-4. No Group C strains hydrolyse sodium hippurate. Many of them 

 grow on 10 per cent, bile agar, but few on 40 per cent, bile agar. On the basis of their 

 action on trehalose and sorbitol Group C streptococci can be differentiated into three 

 sub-groups (Edwards 1934). One of these sub-groups ferments neither trehalose nor 

 sorbitol, another ferments sorbitol but not trehalose, a third ferments trehalose but 

 not sorbitol. 



There is a correlation between fermentation reactions and habitat that gives to these 

 sub-groups an importance that they would not otherwise possess. Most of the strams 

 belonging to the trehalose-negative, sorbitol-negative sub-group have been isolated from 

 horses, particularly from cases of strangles, though they have also been obtained from 

 infections in other animals. They are further differentiated from the groups of strepto- 

 cocci that have been described above by their failure to ferment lactose. They share with 

 these other groups the ability to ferment salicin, and the inabihty to reduce methylene 

 blue in milk. This sub-group clearly corresponds in its biochemical characters to the 



