272 STREPTOCOCCUS-PNEUMOCOCCUS GROUP 



of solid calcium carbonate (marble) to sugar media is important; 

 it neutralizes the excess of acid, and also appears to add somewhat to 

 the nutritive value of the medium. 1 



Streptococci grow slowly in plain broth, producing a sediment after 

 twenty-four to forty-eight hours' incubation. A flocculent sediment 

 consisting of long chains of organisms is characteristic but not distinc- 

 tive of many virulent strains (Streptococcus conglomeratus) ; a 

 granular sediment usually contains short-chain streptococci almost 

 exclusively. 



Streptococcus pyogenes ferments dextrose, lactose, maltose and 

 saccharose and sorbite with the formation of considerable amounts of 

 acid. Mannite is not as a rule attacked. Milk is coagulated in from 

 three to five days, the coagulum resulting from the accumulation of 

 the acid fermentation of the lactose. The coagulum is never dissolved. 

 Andrewes and Horder 2 state that Streptococcus pyogenes does not 

 coagulate milk, although the organism produces a considerable amount 

 of acid in this medium. Smith and Brown 3 have shown that boiling 

 the milk may be necessary to make the coagulum visible. 



Streptococcus pyogenes is an aerobic, facultatively anaerobic 

 organism. Pathogenic strains do not as a rule grow below 16 to 18 

 C. The optimum temperature lies between 35 and 39 C., the maxi- 

 mum about 44 C. The parasitic types are not long-lived away from 

 the human body. Exposure to 60 C. for one hour will kill most 

 streptococci; a longer time is required if the organisms are exposed 

 in albuminous media. Five per cent, carbolic acid and 1 to 1000 mer- 

 curic chloride will kill the naked germs in from five to ten minutes. 

 Streptococci dried in sputum will resist a temperature of 100 C. 

 (in flowing steam) for several minutes, and drying at ordinary tem- 

 peratures in the dark for several weeks. Direct sunlight kills them in 

 about ten hours. The organisms survive and retain their virulence 

 if they are suspended in sterile, defibrinated blood and kept in the 

 ice box for several weeks. 



Products of Growth. Chemical. Streptococci exhibit but little 

 evidence of proteolytic activity. No indol, skatol, phenol or other 

 aromatic derivatives of amino acids have been detected in cultures; 

 gelatin is not liquefied and casein and coagulated blood serum are 

 not visibly changed. Emmerling 4 found peptone, leucin, tyrosin, 



1 Bolduan, New York Med. Jour., 1905, May 13. 



2 Lancet, 1906, ii, 708. 



3 Jour. Med. Research, 1914, xxxi, 455. 

 * Berl. chem. Gesell., 1897, 1863. 



