318 AGRICULTURAL AND INDUSTRIAL BACTERIOLOGY 



motile, do not produce spores, stain readily with the 

 ordinary aniline dyes and are Gram-positive. 



Distribution. The staphylococci are quite common 

 upon the skin and hair in man and animals, likewise in the 

 nose and mouth and occasionally in the feces. They are not 

 uncommon in water, especially when this has been contam- 

 inated with sewage. They are present in many cases of 

 local infection accompanied by pus production. 



Cultural Characters. These bacteria may frequently 

 be secured in pure culture directly from the pus of suppurat- 

 ing wounds, boils or abscesses. The bacteria grow readily 

 upon the ordinary culture media. In gelatin a slow lique- 

 faction occurs. The two species may be differentiated from 

 each other in general by the color produced upon media. 

 "When grown upon potato, for example, Staphylococcus 

 aureus produces a bright orange pigment while the Staphy- 

 lococcus albus is white. Growth in milk is followed by the 

 production of some acid and ultimate digestion of the curd. 



Physiology. Small amounts of acid are produced from 

 some sugars, but no gas. Nitrates are reduced to nitrites. 

 Enzymes capable of digesting casein and gelatin have been 

 demonstrated. 



Pathogenesis. The staphylococci in general produce 

 infections such as abscesses, carbuncles, boils, acne, fur- 

 uncles in man, wound infection, poll-evil and fistula in the 

 horse, and similar lesions in other animals. Inasmuch as 

 these bacteria are normally present upon the surface of the 

 skin, they generally invade the tissues whenever there is a 

 break in the skin, that is, through any injury. They are 

 therefore, the common causes of wound infection or sup- 

 puration in wounds. A boil results from the entrance of 

 organisms of this group under the skin, where they grow 

 (providing the individual is not sufficiently immune) and 

 destroy a certain amount of tissue. A reaction or inflam- 

 matory condition is set up immediately about the injured 



