BACILLUS MALLEI 343 



The Glanders Bacillus 



The glanders bacillus (B. mallei) is an obligatory parasite 

 with the equine species for its normal host. It hardly 

 grows on artificial media below about 20 C., and probably 

 cannot maintain a saprophytic existence outside the 

 animal body. 



Morphology. The glanders bacillus occurs in the 

 tissues as a cylindrical rod with rounded ends, varying 

 between 2 //, and 5 /m in length, and generally straight, 

 though sometimes slightly curved. The bacilli are usually 

 irregularly scattered, and do not tend to form colonies. 

 In stained preparations they often appear more or less 

 beaded, or may exhibit bipolar staining, but some stain 

 uniformly. The bacilli from young cultures not more 

 than twenty- four hours old are almost always short rods, 

 a little thicker than those found in the lesions (Plate XI. a). 

 In old broth cultures the surface growth is largely com- 

 posed of filaments, which do not show any regular seg- 

 mentation, but may exhibit lateral branching, and may 

 have club-shaped extremities. From these features some 

 have inferred that the glanders organism belongs to the 

 Streptothricce. The bacillus does not form spores, and is 

 probably non- motile, though in a hanging- drop prepara- 

 tion a very active Brownian movement is present. 



Staining reactions. The bacillus is Gram- negative, and 

 is not acid-fast, but from young cultures stains readily 

 with the ordinary anilin dyes. In smears of glanders or 

 farcy material, a simple staining with any of the basic 

 anilin dyes, with subsequent decolorisation with dilute 

 acetic acid, suffices to demonstrate it if it is present in any 

 number, a difficulty in recognising the organism being the 

 presence of deeply staining nuclear detritus. In sections, 

 methylene-blue staining with decolorisation in dilute 

 acetic and mordanting with tannin gives the best results 



