226 BACTERIOLOGY FOR NURSES 



Morphology and Staining. The bacillus is a small rod straight 

 or slightly curved with rounded or pointed ends, ranging from 1.5 

 to 5 /A in length and 0.25 to 0.5 /* in width; it usually occurs 

 singly but may occasionally be seen in pairs or long filaments. 

 The organism is non-motile and does not form spores ; it does not 

 stain readily with the ordinary aniline dyes and is Gram negative. 



Cultivation. Growth occurs on ordinary culture media be- 

 tween 22 and 43 C. ; a slightly acid reaction to phenolphthalein 

 and the addition of glycerin greatly favors development. Stroke 

 cultures on agar or glycerin agar at 37 C. are somewhat trans- 

 parent and of a grayish white color and a rather slimy consistency. 

 On agar plates colonies appear as round transparent droplets; 

 in broth a diffuse cloudiness appears which later collects at the 

 bottom of the tube as a heavy viscous sediment. Growth on 

 potato is particularly characteristic ; about the third day a yellow- 

 ish transparent layer, somewhat like clear honey, is visible; as 

 growth continues the color deepens until by the seventh or eighth 

 day it is of a chocolate-brown color while the surrounding potato 

 has acquired a greenish yellow tint. 



Resistance. B. mallei like other vegetative forms is only 

 feebly resistant to heat and antiseptics. It is killed by exposure 

 to moist heat at 55 C. in ten minutes and in a 5 per cent solution 

 of carbolic acid in from three to five minutes. It is somewhat 

 resistant to drying. It has been found to retain its vitality for 

 fourteen days in a dry condition. 



Pathogenesis. As already stated, glanders occurs chiefly 

 among horses; sheep, goats, swine, and rabbits are relatively 

 less susceptible, cattle are immune. 



The disease occurs in man as a result of the direct contact of 

 a wound or skin abrasion with the discharges or diseased tissues 

 of an infected animal. Consequently only those who come directly 

 in contact with horses are likely to be affected. In animals the 

 lesions are of two types, usually spoken of as " glanders " and 

 " farcy." In glanders proper the nasal mucous membranes 

 become inflamed and a profuse catarrhal discharge appears. 

 Very soon firm translucent nodules are formed which later soften 



