CHAPTER X 

 MENINGOCOCCUS 



(DIPLOCOCCUS INTRACELLULARIS MENINGITIS, 

 WEICHSELBAUM) 



The meningococcus occurs in the nose and perhaps the throat of some ap- 

 parently healthy persons and occasionally in the nose of one suffering with 

 meningitis. 



Morphology. The meningococcus is about the same size as staphylococci, 

 but marked variations in size are observed in organisms obtained from the same 

 source. They are arranged in pairs and are shaped like a coffee bean, oval with 

 flat sides in apposition. The meningococcus stains with all the usual anilin 

 dyes and is Gram negative. A peculiarity in staining sometimes observed is 

 that different organisms in the same smear vary in staining, some being faintly 

 stained and others deeply stained. Some observers have noted granular stain- 

 ing, one portion of a coccus staining more deeply than another. 



The meningococcus is non-motile. 



Growth. The meningococcus is an obligate aerobic organism. Develop- 

 ment on culture media occurs only at temperatures between 25C. and 42C.; 

 best at 37C. When a number of tubes of culture media are planted with men- 

 ingococci obtained from the nares or spinal fluid only a few show growth. 

 Meningococci which have led a saprophytic existence on culture media and 

 have been transplanted several times possess a greater aptitude to grow on 

 culture media; cultures from them nearly always show growth. Several cubic 

 centimeters of pus or spinal fluid containing meningococci must be planted on 

 media to obtain growth, even when microscopic examination discloses the pres- 

 ence of many organisms in the fluid. 



Wherry and Oliver, also Cohen and Markle, state that partial oxygen ten- 

 sion cultures, made by connecting culture tubes with slant agar cultures of 

 bacillus subtilis, with rubber hose, show abundant growth of meningococci and 

 gonococci when aerobic cultures show scant and anaerobic cultures no growth. 



Agar. If growth occurs, transparent, pin-point-sized, round colonies appear 

 in 24 hours, they become grayish and opaque in the center and remain discrete. 

 After several days they die. 



Glycerin agar shows the same character of growth as plain agar. 



Blood-serum Agar, ascitic-fluid agar and blood-smeared agar are more 

 favorable media for cultivation than plain agar and show a more luxuriant 

 growth. 



Loeffler's blood serum is the best solid medium for cultivation of the 

 meningococcus. Pin-point grayish colonies appear in 24 hours, as on agar; the 

 growth may become confluent. 



68 



