218 VETERINARY BACTERIOLOGY 



nature. No practicable method of immunization, either by the 

 use of vaccines or antisera, has been developed. 



Bacteriologic Diagnosis. The most conclusive method of 

 bacteriologic diagnosis is by isolation and cultivation of the organ- 

 ism. A demonstration of the characteristic lanceolate, capsulated, 

 gram-positive diplococci is often diagnostic. The agglutination 

 test is not conclusive. 



The relationship of this organism to pleuropneumonia and 

 contagious pneumonia in equines is uncertain, and further work 

 needs to be done before the connection can be made clear. 



Micrococcus meningitidis 



Synonyms. Diplococcus intracellularis meningitidis; Micro- 

 coccus weichselbaumii ; Streptococcus meningitidis; meningococcus. 



Disease Produced. Epidemic cerebrospinal meningitis in 

 man. 



Weichselbaum, in 1887, first adequately described this organism 

 from meningeal exudate, and proved its pathogenic nature by 

 animal experimentation. It has since been observed repeatedly 

 in many epidemics, both in Europe and America. 



Morphology and Staining. Micrococcus meningitidis in stained 

 smears of meningeal exudate usually appears as a diplococcus, 

 or in groups of four. In culture-media it is about 1 /w in diameter, 

 and is usually in pairs, rarely in short chains. The latter fact 

 would seem to indicate that this organism should be classed as a 

 Streptococcus, but the tetrad formation sometimes seen seems, 

 on the contrary, to show that cell division may be in two planes, 

 hence the use of the generic name, Micrococcus. No capsules 

 are produced. It stains readily with the ordinary anilin dyes, 

 but is gram-negative. 



Isolation and Culture. The organism may be obtained by a 

 lumbar puncture with a sterile hypodermic needle, and transferred 

 directly to artificial media. It is best to use a medium containing 

 serum for the first isolation, for this bacterium frequently does not 

 grow well on artificial media at the first. Upon blood-serum 

 at 37 white, viscid, coherent colonies develop. Serum may be 

 added to agar or bouillon and will be found to favor the growth. 



