682 STREPTOCOCCUS 



Str. equi of many authors. According to Bazeley and Battle (1940) all strains of this 

 sub-group fall into one serological type — Type 1. The second sub-group ferments sorbitol 

 but not trehalose, and fails to reduce methylene blue in milk. Serologically, it comprises 

 two types. Type 2 is the more numerous, and is distinguished by fermenting lactose. It 

 has been isolated from respiratory catarrh of horses, and from a variety of lesions in horses, 

 cattle, guinea-pigs, rabbits and so on. Type 3 does not ferment lactose, and was found 

 by Bazeley and Battle only in equine respiratory catarrh. 



There is as yet no evidence that streptococci belonging to this, or to the preceding, 

 sub-group are pathogenic for man. 



The third sub-group is characterized by the fermentation of trehalose but not of sorbitol. 

 The strains belonging to this sub-group have been derived both from animal and human 

 sources, and it seems clear that some strains at least are pathogenic for man. Three of 

 Griffith's 27 types of human-pathogenic, hsemolytic streptococci belong to this C sub- 

 group, not to Group A. All strains of this sub-group are recorded as fermenting salicin, 

 but the action on lactose appears to vary. The results recorded by Edwards (1934) and 

 by Hare (1935) suggest that many of the animal strains fail to ferment lactose, while 

 almost all the human strains act on this sugar. Among equine strains Bazeley and Battle 

 (1940) found that the great majority did not ferment lactose ; these fell into their sero- 

 logical Type 4. A few, which did ferment lactose, fell into Type 5. Simmons and Keogh 

 (1940), who studied 169 strains of human origin falling into the trehalose-positive sorbitol- 

 negative sub-group, were able to divide them into seven further sub-groups on the basis 

 of lactose, sesculin, amygdahn and raffinose fermentation ; these bore some relation to 

 the eight serological types — Types 7, 20 and 21 and five new types — which they were 

 able to distinguish by agglutination. 



The labelling of Group C haemolytic streptococci presents a problem of some 

 difficulty. There is no specific name that can be applied to the group as a whole. 

 One sub-group of strains, however, does seem to merit special attention, namely 

 the group of trehalose, sorbitol and lactose-negative strains, responsible for strangles 

 in horses, which produce characteristic colonies, and fall into Bazeley and Battle's 

 serological Type 1. If Bazeley and Battle's findings are confirmed, then it may 

 be justifiable to apply the specific designation Str. equi to this sub-group. The 

 term Str. dysgalactice is in common use among veterinary bacteriologists to denote 

 a non-haemolytic streptococcus responsible for some cases of acute or subacute 

 mastitis in cattle (see Minett 1936, Stableforth 1942). According to Stableforth 

 (1945) this organism contains the Lancefield Group C carbohydrate, and should 

 therefore be included with the other strains that we have just described. Its exact 

 relationship, however, to these strains is still under study and the specific name 

 that it has been awarded should be regarded as provisional only. 



Group D. 



Great confusion has existed in the past between (a) the hsemolytic streptococci 

 falUng into Group D, (6) the enterococci — usually non-haemolytic — isolated from 

 human faeces, and (c) the lactic streptococci — also non-haemolytic — so frequently 

 present in milk. 



Group D hcemolytic streptococci. — Lancefield (1933, 1941) has recognized a group of 

 haemolytic streptococci that are characterized by the possession of a specific polysaccharide 

 antigen. These organisms are generally known as Group D haemolytic streptococci. 

 They have been isolated mainly from cheese and from human faeces. Morphologically, 

 they tend to assume the diplococcal rather than the streptococcal formation. On horse- 

 blood agar they give rise to /J-hsemolytic colonies. Some, at least, of the strains are capable 

 of producing a filtrable hajmolysin under special conditions (Todd 1934, Plummer 1941). 



