4IO BIOLOGY OF THE LABORATORY MOUSE 



Cultures from 6 of 25 mice autopsiecl and from 12 of 15 guinea pigs 

 showed Brucella hronchiseptica {B. hronchise pticus) . This organism is a gram- 

 negative, motile, cocco-bacillus which grows on ordinary media but does not 

 produce acid or gas from carbohydrates. An alkaline reaction is produced in 

 litmus milk, and ammonia is formed from urea and asparagin. Neither 

 hydrogen sulphide nor indol is formed. 



As Keegan points out, the low incidence of positive cultures in mice 

 may have been due to the fact that tracheal cultures were not made. On 

 the other hand, B. hronchiseptica is not a highly pathogenic organism and is 

 frequently associated with other agents such as viruses — in canine distemper, 

 for example. 



A pathologically similar condition which occurred spontaneously in 

 chronic form in approximately 3 per cent of stock mice has been reported b}' 

 Branch and Stillman (28, 29). No attempt was made to isolate the etio- 

 logical agent. The chief lesion is one of pulmonic consolidation occurring 

 irregularly in the various lobes but most often involving the right medial 

 lobe. Lesions may be multiple or may involve the whole of a single lobe. 

 Early in the disease the affected areas appear red, firm, dry, and hepatized; 

 later they become greyish, gelatinous, and translucent in appearance, and 

 the surface is irregularly granular and puckered. Pleurisy is rare. The 

 peribronchial lymph nodes are enlarged and the lesions tend to follow and 

 persist in the peribronchial and perivascular tissue. Microscopically, the 

 bronchial exudate contains many polymorphonuclear leukocytes, whereas 

 the areas of alveolar consolidation consist largely of mononuclear cells. 

 Fibrin is rarely found. Focal areas of necrosis are occasionally found. 



The same disease occurs sporadically in the stock animals at the Jackson 

 Memorial Laboratory. It progresses slowly and is recognized in the late 

 stages by failure of the animals to thrive and breed, roughening of the fur, 

 weight loss, rapid labored breathing, and finally death. Investigations are 

 being carried out to determine the etiological agent and the possible rela- 

 tionship of B. hronchiseptica. 



Infection due to a Friedlander-like bacillus. — During the course of his 

 investigations on experimental epidemics of mouse typhoid, Webster (318, 

 319) encountered two outbreaks of respiratory infection due to a Friedlander- 

 like bacillus. The disease first appeared in the summer (August) , recurred 

 in successive waves of decreasing severity, and disappeared in the spring. 

 The morbidity and mortality were high. 



The clinical manifestations varied; some animals developed pulmonary 

 involvement, others septicemia, nasal infection, or the carrier state. The 



