CHAPTER XXI 



THE STAPHYLOCOCGI (MICROCOCCI) 



THE power to incite purulent and sero-purulent inflammations and 

 localized abscesses in man and animals is possessed by a large variety 

 of pathogenic bacteria. Most infections, in fact, in which the rela- 

 tive virulence of the incitant and the resistance of the infected 

 subject are so balanced that temporary or permanent localization 

 of the infectious process takes place are apt to be accompanied by 

 the formation of pus. The large majority of acute and subacute 

 purulent processes, however, are caused by the members of a well- 

 defined group of bacteria spoken of as the pyogenic cocci. Among 

 these, pre-eminent in importance, are the " staphylococci" or "micro- 

 cocci." 



Many of the earlier investigators of surgical infections had seen 

 small round bodies in the pus discharged from abscesses and sinuses 

 and had given them a variety of names. Careful bacteriological 

 studies, however, were not made until 1879 and the years imme- 

 diately following, when Koch, Pasteur, Ogston, 1 and others not only 

 described morphologically, but cultivated the cocci from surgical 

 lesions of animals and man. Of fundamental importance are the 

 studies published by Rosenbach 2 in 1884, in which the technical 

 methods of modern bacteriology were brought to bear upon this sub- 

 ject for the first time. The group of staphylococci so named from 

 their growth in irregular, grape-like clusters is made up of several 

 members, by far the most important of which, pathologically, is the 

 Staphylococcus pyogenes aureus. 



STAPHYLOCOCCUS PYOGENES AUREUS 



Morphology and Staining. This microorganism, the most fre- 

 quent cause of abscesses, boils, and many surgical suppurations, is 

 a spherical coccus having an average diameter of about 0.8 micra, 



1 Ogston, Brit. Med. Jour., 1881. 



2 Rosenl)acli, f ' Microorganismen bei Wundinf ektion, " 1884. 



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