VIRULENCE AND BACTERIAL INFECTION 



(Derived from data presented in J. Infect. Dis. 110:201-209. 1962.) 



cent (16 of 32) survived at25°C (P<0.02). This difference was abol- 

 ished by the fourteenth day. With infectious doses as low as 500 

 cells or as high as 5 million cells, both survival time and survivor- 

 ship of mice infected with SR-U were largely independent of the en- 

 vironmental temperature at which the post- infection period was 

 spent. 



Infection with Staphylococcus 



Mice were infected intravenously with 10° cells of a relatively 

 avirulent variant culture of Staphylococcus aureus , Giorgio. They 

 were placed immediately after infection at 5° C, 15° C, or 25° C, 

 After 14 days, 9 per cent (2 of 22) survived at 5° C, 36 per cent 

 (8 of 22) survived at 15° C, and 79 per cent (19 of 24) survived at 

 25 C, Thus with this particular organism, survival was decreased 

 significantly by 5° C (P =0.001) or 15° exposure (P =0.01) when 

 compared to that at 25° C (Table IV). 



Mice injected intravenously with 10 virulent Staphylococci were 

 about equally susceptible both as to survivorship and survival time 



221 



