PREVITE AND BERRY 



5° C and 25° C. Three often animals survived at each temperature, 

 and the mean survival times were 2,9 days at 5° C and 3.6 days at 

 25° C. 



With a smaller infectious dose of virulent cells (500 bacteria), 

 four of eight mice survived at 5° C while six of eight were alive at 

 25° C within 14 days of the initial infection (P>0.05), Once again as 

 with salmonellosis, the more virulent organism seems to produce 

 a fatal infection with little influence from the environmental tem- 

 peratures at which the animals were housed. 



Injection of Staphylococcal Toxin 



A total of 16 mice were injected intravenously with 0.1 ml of a 

 1:32 dilution of a staphylococcal toxin derived as a sterile filtrate 

 from a viscose diffusion chamber in which the bacteria had been 

 grown as described previously. Ten were placed at 5° C and the 

 remainder were held at 25° C. Three died at 5° C and none at 25 C. 

 For the number of animals involved this is not significant. However, 

 if all mice previously given this amount of toxin (by Mr. E. D. 

 Houser) at room temperature are added to the 25° C group (a total 

 in excess of 30, none of which died), it would suggest that cold sen- 

 sitizes mice to Staphylococcal toxins. The limited supply of toxin 

 prevented a more extensive test. 



Heat-killed S. T3^himurium 



Groups of 10 mice were given graded numbers of pasteurized 

 S. typhimurium intraperitoneally. The LDcq dose at 5° C was 8 x 

 10° cells while at 2 5° C, it was 2 x 10^ cells. Thus, cold exposure in- 

 creases 2 50 -fold the lethal effects of heat- killed salmonellae. 



Two groups of mice were then acclimatized to 5° C and 25° C for 

 28 days. At the end of this period, 1.6 x 10® heat-killed cells were 

 injected, and both groups of mice were placed at 5° C. Nine of ten 

 cold acclimatized mice survived, while only two of ten non-cold 

 acclimatized animals lived (P = 0.008). However, 20 per cent or 

 more of the original group of mice at 5° C usually die during a 



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