92 STUDY AND IDENTIFICATION OF BACTERIA. 



CHROMOGENIC BACILLI. 



These are identified by the color of their colonies on agar. The 

 B. pyocyaneus is the most important one of them in medicine, but 

 the B. prodigiosus is also of interest medically. A violet chromogen, 

 the B. violaceus, which is motile and liquefies gelatin, has been de- 

 scribed under many names. It has been found in water. 



An orange-yellow chromogen, the B. fulvus, is nonmotile and 

 varies as to its liquefaction of gelatin. 



B. pyocyaneus (Gessard, 1882). This organism is frequently 

 termed the bacillus of green or blue pus. It is a small (2.5 x .$/*) 



FIG. 35. Bacillus pyocyaneus. (Kolle and Wassermann.) 



motile Gram negative bacillus. It grows readily at room or incubator 

 temperature. It liquefies gelatin rapidly. The green color diffuses 

 through the agar or gelatin on which it grows, so that we not only 

 have the green-colored colony, but the medium as well is colored. 

 Upon potato the colonies are more of a dirty brown. It is widely 

 distributed in water and air, and is frequently isolated from faeces. 

 The B. fluorescens liquefaciens of water seems to be simply a strain 

 of B. pyocyaneus. The B. pyocyaneus is frequently associated with 

 other pus organisms in abdominal abscesses. In addition to having 

 an endo toxin, it produces a soluble toxin similar to diphtheria toxin. 



