SECONDARY BACTERIAL INFECTION IN MICE 

 Number of mice dead/total tested in mice group housed at 



50 C 



6/10 60% 



25° C 



17/30 56.6% 



Table I. The LD-. dose of S. typhimurlum for mice as influenced by bacterial strain 

 and environmental temperatures. 



Inoculum Temperature LD 



50 



Strain RIA 25° C U.l x 10^ 



Strain RIA 5° C 3.8 x 10^ 



Strain SR-11 25° C 7 cells 



Strain SR-11 5° C 7 cells 



Table II. Effect of group housing on survival of mice at 5° C and 25° C infected with 

 4.8 X 10^ cells of S. typhimurium , strain RIA. Single housing, LD,^ « 3.8 x 10^ RIA 

 at 5° C. Single housing, LDgQ - 4.1 x 10^ RIA at 25° C. 



on huddling or activity. They were inoculated with 4.8 x 10^ cells of 

 strain RIA and for those maintained at 25° C, 17 out of 30 (56.6 per 

 cent) died (Table II), This was the anticipated result since this 

 inoculum is the approximate LD5Q for mice at room temperature. 

 On the other hand, mice similarly housed and inoculated and placed 

 at 5° C showed six out of 10 deaths (60 per cent) in response to an 

 inoculum that is characteristically 100 times the LDgQ for animals 

 housed individually in the cold. From these findings it is apparent 

 that cold modifies the response of mice to infectious challenge only 

 under specific conditions of exposure. This is important to keep in 

 mind in comparing the experiments described here with those 

 reported elsewhere. 



In another experiment utilizing 20 normal mice, 10 were shaved 

 on their dorsal and ventral surfaces and housed individually; the re- 

 maining 10 were also shaved but were group housed with pine 

 shavings as bedding. In 24 hours, eight of the 10 mice housed indi- 

 vidually died and all were dead by the fifth day. The group housed 

 mice, however, lived for the entire 14 day experimental period and 

 were then sacrificed. This points up once again the importance of 

 housing conditions in experiments on cold, 



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