PREVITE AND BERRY 



posed to 5° C, 15° C, and 25'^ C. (Derive<l from data presented in J. Infect. Dis. 110; 

 201-209. 1962.) 



S^. typhimurium , strain SR-U. The animals were divided into three 

 groups and placed without delay at 5° C, 15° C, and 25° C. The re- 

 sults in Table II demonstrate no significant difference in survivor- 

 ship and the mean survival times were, in order of increasing tem- 

 perature, 5.4, 5.3, and 4.7 days. Cold was thus without influence 

 either on survivorship of survival time of mice infected with this 

 particular dose and strain of Salmonella. 



The effect of graded doses of SR-U was then evaluated in order 

 to determine whether an effect of temperature on the infectious pro- 

 cess may have been masked by an overwhelming infection. Mice 

 were infected with seven different doses of bacteria, ranging from 

 500 to 5 million cells and then placed at 5° C,,15° C, and 25° C. The 

 animals were more successful, temporarily, in resisting the lethal 

 effects of the virulent salmonellae when housed at room tempera- 

 ture (Table III). At seven days after infection with 20,000 SR-U only 

 18.2 per cent (6 of 33) of the mice survived at 5° C, whereas 50 per 



220 



