270 Wound Infection; Suppuration 



Isolation. The isolation of the organism is simple, the 

 ordinary plate method being a satisfactory means of securing 

 it from pus or other discharges containing it. 



Cultivation. Colonies. The superficial colonies upon 

 gelatin plates are small, irregular, slightly greenish, ill- 

 defined, and produce a distinct fluorescence of the neigh- 

 boring gelatin. 



Microscopic examination shows the superficial colonies to 

 be rounded, and coarsely granular with serrated or slightly 

 filamentous borders. They are distinctly green in the center 

 and pale at the edges. The colonies sink into the gelatin as 



fill 





Fig. 79. Bacillus pyocyaneus. Colonies upon gelatin (Abbott). 



the liquefaction progresses. Four or five days must elapse 

 before the medium is all fluid. 



Gelatin Punctures. In gelatin puncture cultures the 

 chief development of the organisms occurs at the upper 

 part of the tube, where a deep saucer-shaped liquefaction 

 forms, slowly descending into the medium, and causing a 

 beautiful fluorescence. At times a delicate scum forms 

 on the surface, sinking to the bottom as the culture ages, 

 and ultimately forming a slimy sediment. 



Agar-agar. Upon agar-agar the growth developing all 

 along the line of inoculation at first appears bright green. 

 The green color depends upon a soluble pigment (fluorescin) 

 which soon saturates the culture medium and gives it the 

 characteristic fluorescent appearance. As the culture ages, 

 or if the medium upon which it grows contain much 

 peptone, a second blue pigment (pyocyanin) develops, and 

 the bright green fades to a deep blue-green, dark blue, or 



