THE HEMOLYTIC STREPTOCOCCI : GROUP D 



585 



Both tests should be conducted in glucose lemco broth. In the 45° C. test the temperature 

 of the water-bath must be controlled to ^0-1° C. ; in the pH 9-6 test, the reaction of the 

 medium must be adjusted immediately before use, the tubes should be incubated in an 

 anaerobic jar containing soda lime, and the pH of uninoculated control tubes should be 

 checked by the glass electrode immediately before and after incubation. Provided that 

 the tests are carried out under as standard conditions as possible, and that complete 

 uniformity in every respect is not insisted on, it is often possible to allocate individual 

 strains to one or other group (Table 38). 



TABLE 38 

 Differentiation of Str. fcecalis and Str. lactis 



Since the lactic streptococci belong to a different serological group (Group N), 

 they need not be considered here. Group D hsemolytic streptococci and entero- 

 cocci require a little further discussion. Numerous species have been recognized 

 and named among these organisms. 



Str. zymogenes, for example, of MacCaUum and Hastings (1899), which is hsemolytic, 

 ferments mannitol, hquefies gelatin and digests casein, appears to correspond to the former 

 group, and Str. fcecalis of Andrewes and Horder (1906) to the latter group. Str. lique- 

 faciens of Orla- Jensen (1919) resembles Str. fcecalis, but hquefies gelatin and digests casein. 

 Str. durans of Sherman and Wing (1937) is /J-hsemolytic, grows at 50° C, but does not 

 usually ferment either mannitol or sorbitol. Str. glycerinaceus differs from Str. fcecalis 

 in fermenting glycerol. Str. bovis and Str. inulaceus (see Orla-Jensen 1919, Ayers and 

 Mudge 1923) resemble each other in fermenting raffinose but not mannitol ; their relation 

 however, to the enterococci is still in doubt. 



In considering the nomenclature of this group, we must determine whether 

 any single species can be defined rigidly enough to enable it to be recognized and 

 distinguished from other species by tests that yield consistent results. Unless 

 we can do this, the use of a specific name tends to be misleading rather than helpful. 

 We think that it is now possible to define broadly Str. fcecalis in this way. Ignoring 

 the absence of haemolysis, we see that the enterococci differ in no important respect 

 from Group D hsemolytic streptococci. We should therefore define Str. fcecalis 

 as a coccus arranged in pairs or very short chains, growing in the presence of bile 

 salt, usually resisting heat at 60° C. for 30 minutes, almost always fermenting 

 lactose, mannitol, salicin, and usually sucrose, trehalose and sorbitol, but not 

 raffinose or inulin, reducing the dye and forming a solid clot in litmus milk, and 

 possessing the specific Group D polysaccharide ; subsidiary characters being the 

 failure of most strains to hydrolyse sodium hippurate, the production of a low 

 pH (4-0-4-8) in glucose broth, and the ability to grow at temperatures between 

 10° and 45° C, in skimmed milk containing 1 : 1,000 methylene blue, in lactose 



