368 GLANDERS ANTHRAX PYOCYANEUS 



nosis upon morphological examination alone. The Gram stain will 

 distinguish between the two, however. 



Isolation and Culture. Bacillus mallei grows well upon ordinary 

 laboratory media, better if glycerin is added, and upon blood serum 

 and potato. The first growth outside the animal body may bp diffi- 

 cult to obtain. Colonies on glycerin agar are small, yellowish and 

 round. At first the growths are translucent, later they become nearly 

 opaque and more deeply colored. Growth in gelatin is slow and not 

 distinctive; no liquefaction takes place. A uniform turbidity appears 

 in broth after twenty-four hours' incubation at 37 C., which gradually 

 settles out as a tenacious, slimy sediment. If the culture is undis- 

 turbed, a pellicle gradually forms on the surface of the medium. 

 Litmus milk is slowly acidified, and coagulation may occur after 

 seven to fourteen days' incubation. Growth on old alkaline potato 

 is distinctive; after twenty-four to forty-eight hours' incubation a 

 light brown, translucent layer appears, which has been likened in 

 color and general appearance to a layer of honey. Later the growth 

 becomes darker, even brownish-red in color, and the underlying potato 

 becomes greenish or even brown. Potato that is acid does not exhibit 

 the typical honey yellow growth. 



The glanders bacillus is aerobic, facultatively anaerobic; the opti- 

 mum temperature of development is 37 C., growth ceases above 43 

 C., and is extremely slow below 25 C. The resistance of the organism 

 to chemical agents is not great, but it remains viable for several weeks 

 when dried in pus or blood and maintained in a cool, dark place. An 

 exposure of naked bacilli to 55 C. for five to seven minutes kills the 

 organisms. 



Products of Growth. Chemical. Bacillus mallei is culturally inert 

 in purely protein media: indol, skatol and other products of degrada- 

 tion of amino acids are not produced. Acid, but no gas, is formed in 

 dextrose broth, and acid is produced in milk. 



Enzymes. No enzymes have been demonstrated in cultures of B. 

 mallei. 



Toxins. Soluble toxins have not been isolated from growths of the 

 glanders bacillus; the poison of the organism belongs to the group 

 of the endotoxins. A substance analogous to tuberculin has been 

 prepared from four to five weeks' glycerin broth cultures of Bacillus 

 mallei, mallein or morvin. The preparation of mallein is essentially 

 the same as for tuberculin. The injection of mallein in moderate 

 doses into normal animals may lead to transient fever and a slight 



