Streptococcus Pyogenes, Rosenbach (1884). 

 STEEPTOCocous EBYSiPELATis, Fehleisen (1883). 



Origin. — In abscesses, pyemia, puerperal fever, erysipelas and 

 many other diseases as indicated below. In erysipelas it is found 

 in the lymphatic vessels of the diseased skin, and only very rarely in 

 the blood and internal organs. Streptococci are found in the mouth 

 and sputum; on the mucous membranes of the nose, urethra, vagina, 

 etc.; frequently present in mixed or secondary infections. 



Form. — Small, spherical cells which may grow in pairs or in 

 short chains of 6-8; not infrequently, as when grown in bouillon, the 

 chains may consist of a hundred or more cells. 



Motility. — Has no motion. 



Sporulation. — None. 



Anilin dyes.— Stain readily; Gram's method is applicable. 



Growth.— Is readily obtained on various media, even at ordinary 

 temperature, but the growth is slow and limited. Alkaline reaction 

 is necessary. Glycerin agar is very useful. 1 part of ordinary 

 bouillon and 2 parts of human blood-serum yields the best medium. 

 In this the virulence is unaltered. 2 parts of bouillon and 1 part of 

 ascitic fluid is useful though not as good as the preceding. 



Plates. — Oti gelatin the colonies develop rather slowly, forming minute oval or round, 

 yellowish-brown, finely granular colonies, which are sharply bordered and usually show 

 concentric rings. Surface colonies remain small. No liquefaction. On agar plates, devel- 

 oped in the incubator, it forms delicate, grayish, translucent, drop^like colonies. . 



Stab culture. — In gelatin the growth is quite characteristic. Along the line of inocu- 

 lation a row of minute colonies forms, which usually remain separate, but may fuse 

 together, giving rise to a continuous line. Scarcely any growth forms on the surface. 



Streak culture. — On as^ar or blood-serum, it develops as minute, scarcely visible, 

 round colonies which resemble minute dew-drops. They do not tend to spread. 



Bouillon. — At 37" becomes diffusely clouded and a slight, whitish sediment forms. .4s 

 a rule, however, the liquid does not cloud but remains clear, in which case the growth 

 occurs on the w^Us and bottom of the tube. 



Milk is coagulated. Acid is produced. Growth on potato is doubtful. 



Oxygen requirements.— Is a facultative anaerobe. 



Temperature.— Grows slowly at room temperature; best at 30-3'7°. 



Behavior to gelatin. — Does not liquefy. 



Attenuation. — The virulence of the organism is subject to con- 

 siderable variation, even when taken directly from a case of the 

 disease. Artificial cultures soon become attenuated and will die out 

 unless transplanted every few weeks. The virulence and vitality can 

 be preserved best by sealing the heart-blood of an infected rabbit in 

 tube pipettes (see p. 279). Vitality is also well preserved in gelatin ' 

 stab culture; or on agar to which human blood has been added. By 

 successive passage through animals, or by the sac method, the viru- 

 lence can be increased so that virtually a single cell is fatal to a rab- 

 bit. Thus, cultures have been obtained of which one hundred mil- 

 lionth of a c.c. was invariably fatal; whereas, a one hundred thousand 

 millionth would kill 1 or 2 out of 4 rabbits. The virulence can be 

 also increased by injection together with Proteus vulgaris. 



Immunity, Pathogenesis. — See p. 383. 



Infection. — Undoubtedly through wounds or injuries of the skin. 



Diagnosis. — The detection of streptococci in blood can be effected 

 by simple or by Gram's stain, supplemented by culture on glycerin agar. 

 It is better to add 2 c.c. of the fresh blood to 4 c.c. of agar and to 

 make Petri plates with this mixture (37°). Intra-peritoneal injection 

 into white mice; intravenous into rabbits. 



364 



