304 



Suppuration 



Gelatin Punctures. — In gelatin the growth occurs along the whole 

 length of the puncture, causing an extensive liquefaction of the 

 medium in the form of a long, narrow, blunt-pointed, inverted cone, 

 sometimes described as being like a stocking, full of clouded liquid, 

 at the apex of which a collection of golden or orange-yellow precipitate 

 is always present in Staphylococcus aureus. It is this precipitate 

 in particular that gives the organism its name, "golden staphylo- 

 coccus." 



Agar -Agar. — The growth of the golden 

 staphylococcus upon agar-agar is subject to con- 

 siderable variation in the quantity of pigment 

 produced. Sometimes, perhaps rarely, it is 

 golden; more commonly it is yellow, often cream 

 color. Along the whole line of inoculation a 

 moist, shining, usually well-circumscribed 

 growth occurs. When the development occurs 

 rapidly, as in the incubator, it exceeds the 

 rapidity of color production, so that the center 

 of the growth is distinctly colored, the edges 

 remaining white. 



Potato. — Upon potato the growth is luxu- 

 riant. Staphylococcus aureus producing an 

 orange-yellow coating over a large part of the 

 surface. The potato cultures may give off a 

 sour odor. 



Bouillon. — When grown in bouillon the organ- 

 ism causes a diffuse cloudiness, with a small 

 quantity of slightly yellowish sediment. The 

 reaction of the medium becomes increasingly 

 acid. Nitrates are reduced to nitrites. 



Milk. — -In milk, coagulation takes place in 

 about eight days, and is followed by gradual 

 digestion of the casein. In litmus milk slow 

 acid production is observed. 

 Thermal Death Point. — Staphylococci are usually quite suscep- 

 tible to the effect of heat, though their resistance is not uniform. 

 Sternberg found them destroyed by an exposure to 62°C. for ten 

 minutes, and to 8o°C. for one and a half minutes, but three cultures 

 studied by von Lingelsheim were not killed by an exposure to 6o°C. 

 for an hour, and one culture studied by him endured an exposure 

 to 8o°C. for ten minutes. 



Metabolic Products. — Staphylococci can make use of free or 

 combined oxygen, hence are aerobic or anaerobic. In liberating 

 combined oxygen, no gas is generated in any culture medium. They 

 produce ferments by which gelatin is liquefied, milk coagulated and 

 digested, blood-serum digested and slowly liquefied. A yellow 

 pigment is produced. Nitrates are reduced to nitrites in cultures 



Fig. io8. — Staph- 

 ylococcus pyogenes 

 aureus. Puncture 

 culture three days 

 old in gelatin (Fran- 

 kel and Pfeiffer). 



