578 STREPTOCOCCUS 



Group B. — The existence of specific types in Group B was first established by 

 Stableforth (1932), who found three serological types among strains from bovine 

 mastitis ; these were sharply distinguished by their precipitation and agglutination 

 reactions. The type-specific antigen was found by Lancefield (1934, 1938) to be, 

 not a protein as in Grouj) A, but a polysaccharide. By precipitation tests she was 

 able to define four specific types. British and Australian investigators (Stable- 

 forth 1937, Stewart 1937, Simmons and Keogh 1940) have carried this study further 

 by separating off, mainly by the agglutination and absorption of agglutinins 

 technique, a number of sub-types. What the antigen or antigens concerned in 

 the agglutination test may be is still a matter for conjecture, but so far as the 

 four main types are concerned, there seems to be agreement between the results 

 of the precipitation and agglutination tests (Slanetz and Naghski 1940, Simmons 

 and Keogh 1940). The notation is still confused, but there is much to be said 

 for Stableforth's suggestion of numbering the main types, as in Group A, and 

 giving small letters to the sub-types, e.g. Type la, lb, Ic, Id, 2a, 3a, 3b, etc. Again, 

 there is disagreement on the identity or non-identity of Group B strains of human 

 and bovine origin. Further work will be required before discrepancies of this sort 

 can be cleared up. 



Group C. — -It has already been mentioned that three of the types of haemolytic 

 streptococci identified by Grifi&th, namely Types 7, 20, and 21, belonged to Group C. 

 Five more types have now been differentiated by the agglutination test among 

 human strains (Simmons and Keogh 1940), and five among equine strains (Bazeley 

 and Battle 1940). There is reason to believe that the type-specific antigen is of 

 protein nature. 



Group D. — This group contains a number of organisms of the enterococcus 

 type, the specific or varietal nature of which will be discussed later (p. 582). By 

 agglutination several types have been distinguished by Japanese and other workers 

 (for references see Grumbach and Schnetz 1938, Ehrismann • 1943). Lancefield 

 (1941) states that she has been able to define three distinct types. The type- 

 specific antigens appear to be of polysaccharide nature. 



Other Groups. — One type has been found in Group E (Lancefield 1941). In 

 Group F Bliss (1937) established four types by precipitation and agglutination 

 reactions, and in Group G one type, which was identical with F Type 1. Simmons 

 and Keogh (1940) were able to distinguish a number of serological types among 

 both the large-colony and the so-called minute forms of streptococci in Group G. 

 One type has been found in Group K (Lancefield 1941). 



Antigenic Structure of the a-Hsemolytic Streptococci.— We know little, as yet, 

 about the antigenic structure of the many species and varieties of a-hsemolytic 

 streptococci that have been described. It seems quite clear that the viridans 

 group of streptococci contains no such polysaccharide group antigens as have been 

 found in the haemolytic streptococci. On the other hand, specific types can be 

 recognized within certain species. Sherman, Niven and Smiley (1943), for example, 

 using the precipitation technique, have found that strains of Str. salivarius fall 

 into two main types and an unknown number of other types. Solowey (1942) 

 likewise, who studied 108 strains of viridans type from subacute bacterial endo- 

 carditis and 99 strains from human throats and extracted teeth, was able to dis- 

 tinguish at least eight different types. The systematic relationship between the 

 different organisms has still to be worked out. 



