THE HEMOLYTIC STREPTOCOCCI : GROUPS E TO N 587 



tinguished by Simmons and Keogh (1940) among both the large colony and the so-called 

 minute forms of streptococci in this group ; and Bliss (1937) has recognized one type, 

 which was identical with her Group F Type 1. 



As regards their other biological and biochemical properties, there appears to be a 

 conflict of evidence in regard to the final pH attained in glucose broth. Plummer (1935) 

 gives this as pH 4-4-4-6, which would place these strains in the " high-acid " group ; 

 but Lancefield and Hare (1935) and Hare (1935) give figures of pH 4-6-5-2. Group G 

 strains do not hydrolyse sodium hippurate. The majority are able to multiply on 10 per 

 cent, bile agar, but few on 40 per cent, bile agar. They do not reduce methylene blue 

 in milk. They ferment trehalose, but not sorbitol. AU strains tested have fermented 

 lactose, but the fermentation of salicin appears to be less constant than with Groups 

 A, B and C. 



Most of the strains that have been identified as belonging to this group have been 

 isolated from man, a few from the monkey or the dog. Several of the human strains 

 have been derived from normal persons, but it seems clear that some, at least, are patho- 

 genic for man, though there is a suggestion that they seldom cause very severe infections. 

 One of Griffith's 27 types — Tyjie 16 — of human-pathogenic haemolytic streptococci falls 

 into this group. 



The labelling of this group should clearly be provisional. It shows obvious 

 relationships to Group C, and, apart from its antigenic structure, to Group A. 

 There seems no reason, at the moment, to allot to it any specific name. " Group G 

 hsemolytic streptococci " will serve our immediate purpose. 



Groups H and K. 



These two additional antigenic groups have been differentiated by Hare (1935). They 

 appear to differ from each other, and from the oth^r groups of hsemolytic streptococci 

 that have been described, in regard to their group-specific antigens. Those strains that 

 have been exammed have shown other cultural or biochemical characters that may have 

 differential significance ; but so few strains belonging to these two groups have yet been 

 studied that it would be premature to describe their characters in any detail. They 

 have all been isolated from the nose or throat of normal persons, and there is as yet no 

 evidence that they are pathogenic. One antigenic type has been recognized in Group K 

 (Lancefield 1941). 

 Groups L and M. 



These groups have been differentiated by Fry (1941), who has been kind enough to 

 supply us with the following information. Most of the original strains studied were 

 isolated by Dr. Tom Hare from animal sources. 



The majority of Group L strains came from dogs and pigs, but two (Hooper and Krone) 

 were isolated from the human throat by White, Rudd and Ward (1939) in Austraha. 

 The colonies are small, but have a wide zone of /S-hsemolysis. A soluble hsemolysin is 

 formed. There is no growth on bile agar, and no hydrolysis of sodium hippurate. Tre- 

 halose is fermented, and sometimes lactose, but not mannitol, saUcin, or sorbitol. 



Strains belongmg to Group M came almost exclusively from the tonsil of the dog ; 

 no human strains have yet been identified. Growth is extremely poor, and the organisms 

 rapidly die out. On blood agar the colonies are very small, but are surrounded by a 

 wide zone of /^-haemolysis. A soluble hsemolysin is formed, but it is weak and acts slowly. 

 Lactose is fermented, but not trehalose, mannitol, salicin, or sorbitol. The formamide 

 method of extraction cannot be used for this group, as heating much above 100° C. destroys 

 the precipitinogen. 

 Group N. 



We have already pomted out, when discussing Group D streptococci (p. 582), that 

 the lactic streptococci can be distinguished from the enterococci by a series of metabohc 

 and heat-resistance tests, and by their failure to form the group-specific polysaccharide 



