CHAPTER XL 

 BACILLUS MALLEI 

 (GLANDERS BACILLUS) 



The bacillus mallei is present in the nasal discharge and saliva of many of 

 those suffering from the disease, also in the exudate from open skin lesions. 

 From such sources the dust and soil of stables and horse troughs are at times 

 polluted. 



Glanders is a disease of horses, asses and mules, occasionally carnivora fed 

 the meat of animals dead of the disease develop glanders, and the disease 

 occasionally afflicts man. 



Infection with glanders is confined almost entirely to persons in frequent 

 contact with horses. 



Morphology. Bacillus mallei occurs both as straight and slightly curved, 

 non-motile rods, 3 ju to 4 ju long, 0.50 /z to 0.75 p wide, having rounded ends, 

 and arranged singly in irregular masses. Old cultures show larger, club-shaped, 

 granular forms, long (apparently branched) filamentous forms, and chains of 

 small coccoid forms. Bacillus mallei does not form spores. 



Staining. This bacillus stains readily with all the common stains and is 

 Gram negative. It can be decolorized, after staining, by washing with water, 

 much easier than other bacteria. As a rule, staining is not uniform, many 

 organisms showing an oval unstained central portion, falsely suggesting the 

 presence of spores. 



Growth. Occurs from 23C. to 4iC., best at 37C. Bacillus mallei is 

 aerobic and only slightly facultative anaerobic. 



Bouillon incubated at 37C. becomes cloudy in 24 hours, later a tough, 

 mucoid, white sediment appears and in several days a white pellicle sometimes 

 covers the surface. 



Agar incubated at 37C. shows surface growth in 20 to 24 hours, at first a 

 white, transparent streak, which spreads, thickens and becomes opaque as 

 growth continues. 



Glycerin agar favors a more abundant growth, the surface usually being 

 covered with a film having the same appearance as observed on plain agar. 



Gelatin. Scant, almost invisible growth occurs upon or in gelatin after 

 several days, it is not liquefied. 



Potato, neutral or nearly neutral in reaction is an important medium in the 

 study of the glanders bacillus. In 48 hours, incubated at 37C., a character- 

 istic, moist, thick, yellowish solid growth develops. As the culture ages it 

 turns brown and the potato adjacent to it becomes black. 



Milk is acidulated and in i to 2 weeks slowly coagulates. 



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