386 PATHOGENIC MICROORGANISMS 



flammations of the upper respiratory tract. It was subsequently care- 

 fully studied by Ghon and H. Pfeiffer.' According to these authors 

 the pathogenic significance of the micrococcus is slight, though occasion- 

 ally it may be regarded as the causative factor in catarrhal inflammations. 

 Its chief claim to attention, however, lies in its similarity to the meningo- 

 coccus and the gonococcus, from neither of which it can be morphologi- 

 cally distinguished. It is decolorized by Gram's stain, appears often in 

 the diplococcus form, and has a tendency, in exudates, to be located 

 intracellularly. Not unlike the two microorganisms mentioned, too, it 

 shows but slight pathogenicity for animals. 



Differentiation from gonococcus is extremely simple in that Micro- 

 coccus catarrhalis grows easily on simple culture media and shows 

 none of the fastidious cultural requirements of the gonococcus. 



From meningococcus the differentiation is less simple and, because 

 of the presence of both microorganisms in the nose, is of great impor- 

 tance. 



Distinction between the two is made entirely upon cultural charac- 

 teristics and agglutination reactions. Culturally, Micrococcus catar- 

 rhalis grows more heavily than meningococcus upon the ordinary 

 culture media. The colonies of Micrococcus catarrhalis are coarsely 

 granular and distinctly white in contradistinction to the finely granu- 

 lar, grayish meningococcus colonies.^ Micrococcus catarrhalis will 

 develop at temperatures below 20° C, while meningococcus will not 

 grow at temperatures below 25° C.^ 



Dunham,* who has recently made a comparative study of meningo- 

 coccus and other Gram-negative diplococci from the nose and throat, 

 states that while some of the supposed Micrococcus catarrhalis cul- 

 tures are easily distinguished from meningococcus simply by the char- 

 acteristics of their growths upon two-per-cent glucose agar, others offer 

 great difficulties to differentiation. He recommends as a differential 

 medium a mixture of sheep serum and bouillon containing one per 

 cent of glucose. Upon this medium all true meningococci produce 

 acid, but no coagulation, with twenty-four hours. Cultures from the 

 nose and throat, however, produce acid and coagulation, or else pro- 

 duce an alkaline reaction. 



> Ghon und H. Pfeiffer, Zeit. f. klin. Med., 1902. 



2 Ghon und Pfeiffer, loc. cit. 



3 Weichselhaum, in Kolle und Wassermann, Bd. iii, p. 269. 

 » Dunham, Jour. Inf. Dis., 1907. 



