Micrococcus Pneumoniae Crouposae, 

 Sternberg, Pasteur (1880). Fraenkel (1886). 



PRAENKEL'S DIPLOCOCCUS, D. LiANCEOLATUS, D. PNEUMONIA, MICEOBE 

 OF SPUTUM SEPTICEMIA. 



Origin. — Occasionally in the saliva and nose of healthy persons; 

 especially frequent in the "rusty" sputum of pneumonia. The same 

 organism, or scarcely disting'uishable varieties, may be present in 

 cerebro-spinal meningitis, pleuritis, peritonitis, pericarditis etc. 



Form.— Occasionally round, usually oval, barley, or lance-shaped 

 diplococci. It may form chains of 4-6 cells, and hence may resemble 

 a streptococcus. Owing to its oval form it is sometimes regarded as 

 a bacillus. In the animal body, it is surrounded by large capsules 

 (Fig. 5, p. 29). These are not present on artificial media. 



Motility. — It has no motion. 



Sporulation. — Unknown. 



Anilin dyes. — Stain readily; so does Gram's method. The cap- 

 sules remain colorless. 



Growth. — Takes place somewhat slowly and only at higher tem- 

 perature, and on alkaline media. The ordinary media are far from 

 being favorable for its growth. This is seen in the more or less 

 marked change in form and size, and especially in the rapid loss of 

 virulence and vitality. 5 per cent, glycerin agar makes an excellent 

 medium. 2-3 per cent, of glucose is also beneficial. It should be 

 transplanted every two or three weeks. 



Plates.^ — On gelatin plates kept at 24°, small, round, sharply defined, slightly granu- 

 lar, whitish colonies develop slowly. On agar plates in the incubator, in 48 hours, the sur- 

 face colonies appear as delicate, glistening, transparent drops which, under the microscope, 

 are round, sharply bordered, finely granular, and usually possess a dark center. 



Stab culture. — In gelatin a row of small, white granules develop along the line of ino- 

 culation. Vitality preserved for some time; acid reaction. Slight growth on the surface. 

 Does not liquefy; resembles in this respect the streptococci. 



Streak culture. — On agar in the incubator, the growth develops as a thin layer of 

 delicate, glistening, almost transparent drops. It dies out rapidly. On blood-serum it 

 forms a transparent film of dew-like drops. No growth on potato. 



Bouillon. — Slight diffuse growth which soon settles yielding a very slight deposit. 



Milk. — Is a favorable culture medium; it may, or may not coagulate. 



Oxygen requirements. — It is a facultative anaerobe. 



Temperature. -Growth occurs only between 24 and 42°. Its opti- 

 mum is about 37°. After repeated cultivation it may adapt itself to 

 a temperature of about 18°. 



Behavior to gelatin. — Does not liquefy. 



Attenuation. — See p, 337. 



Immunity. — This can be obtained by intravenous injection of a 

 very small amount of the virulent culture; by injections of filtered 

 cultures, especially when heated to 60°; blood serum of immune ani- 

 mals has a questionable value. Blood-serum from pneumonic pa- 

 tients has been said to immunize rabbits against the pure culture, 

 but this is doubtful. Injections of nuclein immunize rabbits. 



Pathogenesis. — In rabbits a subcutaneous injection of 0.1-0.2 c.c. 

 of recently isolated bouillon cultures produces death in 24-48 hours. 

 The diplococcus is found in the blood and internal organs and is sur- 

 rounded by a capsule. Tracheal injections in rabbits produce true 

 pneumonia. Mice and rabbits are highly susceptible; guinea-pigs, 

 sheep, dogs and cats are less susceptible. Chicken and doves are 

 immune. 



1 Make glycerin agar Petri dishes from the peritoneal exudate in a rabbit. Make 

 cover-glass preparations from the peritoneum, surface of intestines and from the heart- 

 blood, and stain by the simple, and by Gram's method. 



338 



