THE ROLE OF LOW ENVIRONMENTAL TEMPERATURES IN 

 PREDISPOSING MICE TO SECONDARY BACTERIAL INFECTION^ 



Gennaro J. Miraglia^ and L, Joe Berry 



ABSTRACT 



The LDgQ for mice of S. typhi murium, strain RIA, is 4.1 X 10 5 cells for animals 

 individually housed without bedding and maintained at 25° C. It is 3.8 X 10^ cells for 

 animals similarly housed but kept at 5° C. However, mice are able to withstand nearly 

 100 times this dosage of strain RIA if they are housed in groups at 5° C. Normal 

 mice with their dorsal and ventral surfaces shaved are unable to survive more than 

 a few days when housed individually in the cold, but survivte beyond two weeks under 

 group housing conditions. No effect of cold could be detected in mice infected with the 

 highly virulent SR-ll strain of^. typhimurium since all animals died following infection 

 with only a few cells. Mice that were natural carriers of salmonellae as judged by 

 fecal discharge were highly resistant to challenge and responded to cold in a manner 

 similar to normal mice infected with RIA. Strain RIA could be isolated from the tis- 

 sues of infected animals with greater frequency and persisted longer in mice main- 

 tained at 5° C than those at 25° C. Coagulase negative staphylococci were isolated 

 from liver, lung, spleen, heart, and kidney of animals that survived salmonellosis for 

 14 days at 5° C. The staphylococci did not appear to have a predeliction for one tissue 

 over another, and were isolated in an incidence proportional to the number of salmon- 

 ellae injected in the primary infection. At 25° C, only a small percentage of mice 

 had staphylococci in tissues, and these occurred independent of the infectious dose of 

 salmonellae. These observations were made on normal mice infected with RIA and 

 on carrier mice infected with SR-ll. The origin of the secondary invader remains 

 obscure, but it does not appear to result from a penetration of coagulase negative 

 staphylococci from the lumen of the gut to the deep tissue. Mice devoid of intestinal 

 staphylococci and recolonized with coagulase positive staphylococci continue to show 

 coagulase negative isolates from deep tissue. 



1 This work was supported in part at Bryn Mawr College by Contract AF 4l(657)-340 

 between Bryn Mawr College and the Arctic Aeromedical Laboratory, USAF, and in 

 part by Training Grant 2E-148, U. S. Public Health Service. 



2 Postdoctoral Fellow on TrainingGrant 2E-148. Present address: Department of Micro- 

 biology, Seton Hall College of Medicine, Jersey City, New Jersey. 



271 



