570 STREPTOCOCCUS 



out by Niven, Smiley and Sherman (1942) that, in general, the a-haemolytic streptococci 

 fail to hydrolyse arginine with the production of ammonia, whereas the yS-heemolytic 

 streptococci and the enterococci are able to do so. 



There is also agreement that the fermentation of mannitol is characteristic of the strepto- 

 cocci that normally inhabit the human intestine (see Winslow and Palmer 1910, Fuller and 

 Armstrong 1913, Hopkins and Lang 1914, Dible 1921, Bagger 1926, Meyer 1926, Meyer 

 and Schonfeld 1926, Downie and Cruickshank 1928). These streptococci usually ferment 

 salicm and lactose, seldom inulin or raffinose, and usually clot and decolorize litmus milk. 

 A few of them are peculiar in liquefying gelatin. In relation to this group of streptococci 

 an additional fermentation test was introduced by Rochaix (1924) — -the fermentation of 

 sesculin in a bile-containing medium. This reaction has been studied by Meyer and Schon- 

 feld (1926) and by Weatherall and Dible (1929). It has been found by many workers to 

 be of considerable differential value ; but, as Weatherall and Dible point out, the inclusion 

 of bile salts in the medium removes it from the ordinary category of fermentation tests, 

 since bile salts inhibit the growth of many species of streptococci (see below) and in their 

 absence sesculin is attacked, though often slowly, by many non-faecal species or types. 



Comparing the streptococci of man with those from other animals, several points of 

 interest have emerged. 



Winslow and Pahner (1910), while confirming the frequency of mannitol-fermenting 

 streptococci in human faeces, noted their rarity in fseces from the cow or horse. They 

 found also that raffinose-fermenting strains, while relatively uncommon in human fseces, 

 were very common in the fseces of cattle. Fuller and Armstrong (1913) examined 349 

 strains of streptococci isolated from fseces — 123 from man, 129 from the horse and 97 from 

 cattle. They found that 65 per cent, of the fsecal streptococci from man fermented manni- 

 tol, as compared with 2-3 per cent, of the bovine or equine fsecal strains. Raffinose- 

 fermenting streptococci, on the other hand, were not found among the human fsecal strains, 

 while 12 per cent, of the equine fsecal strains, and 73 per cent, of the bovine fsecal strains 

 fermented this sugar. The equine fsecal strains were characterized by a frequent failure 

 to ferment lactose. 



The fact that streptococci isolated from horses, whether from suppurative lesions or 

 from the mouths or intestines of normal animals, frequently fail to ferment lactose has 

 been noted by many observers (see Jones 1919). 



The importance of milk as a human food, and of the cow as a stock animal, has led to 

 a careful and detailed study of the streptococci that occur in normal milk, or in the milk 

 from diseased animals, or that have been isolated from the udder in acute or chronic mastitis. 



A type of streptococcus that is almost constantly present in milk, and has been given 

 the name Str. lactis, resembles in many ways the streptococcus commonly found in human 

 fseces ; and it will therefore be more convenient to deal with its fermentation reactions 

 when considering its probable relation to that organism in a later section. 



In regard to those streptococci that are associated with mastitis in the cow, acute or 

 chronic, certain additional criteria, based on fermentation reactions, have been introduced 

 within recent years in an attempt to differentiate the characteristically bovine strains from 

 those of human origin. Among these are (1) the final pH produced in glucose broth (Avery, 

 R. C, and Cullen 1919, Ayers and Mudge 1922, Frost et al. 1927, Minett et al. 1929, Avery, 

 R. C. 1929fl, b, Minett and Stableforth 1931, 1934, Lancefield 1933, Hare and Colebrook 

 1934) ; and (2) the capacity to hydrolyse sodium hippurate (Ayers and Rupp 1922 and 

 other references above). It has been found that mastitis strains of human origin produce a 

 final pH of 5-0-5-6 in glucose broth, and fail to hydrolyse sodium hippurate. Bovine strains, 

 on the other hand, produce a final pH of 4-2-4-8 in glucose broth, and hydrolyse sodium 

 hippurate. It has also been found that the fermentation of trehalose and sorbitol afford 

 a valuable criterion in the examination of a particular group of haemolytic streptococci that 

 are found both in men and animals — mainly horses. The human strains in the group 

 usually ferment trehalose but not sorbitol ; the animal strains ferment sorbitol but not 

 trehalose (Ogura 1929, Edwards 1932, 1933, Minett 1935a, b). 



