Chapter 6 



EFFECT OF NEUTRONS ON THE RESISTANCE OF MICE TO 

 STAPHYLOCOCCUS INFECTION 



By J. O. ELY and M. H. ROSS 



Neutron irradiation of animals was found by Lawrence et al. (1, 2) to 

 reduce the white l^lood cell count and to have a profound effect on the 

 lymphoid tissues. Lawrence and Tennant (3) concluded that, after irradi- 

 ation with doses of X-rays or neutrons sufficiently large to result in the 

 death of mice within a few days, infection was not necessarily a finding. 

 When the doses were decreased, however, and the animals lived longer, 

 bacteremia was usually observed. Resistance to infection therefore ap- 

 pears to be reduced in animals exposed to neutron radiation. 



Three groups of 30 mice, of the Detweiler strain, averaging nearly 20 



TABLE I 



Mortality Frequency among Mice Injected ivith Bacteria 



Group 



Irradiated 



Non-irradiated 

 Irradiated 



Total 



30 

 1 

 



grams, were allowed water and food ad lib. Two of these groups were 

 irradiated with 84.6 n in Box No. 7 (Enns et al. (4)). 



The organisms of a strain of hemolytic Staphylococcus aureus, grown 

 on Difco heart infusion broth (agar slants), were removed 18 to 20 hours 

 after seeding by washing with 0.85 per cent NaCl solution. This sus- 

 pension of organisms was injected intraperitoneally, one injection approx- 

 imately 20 hours after completion of irradiation and another 24 hours after 

 the first injection. The amount of bacteria injected was the same for all 

 mice. 



Group I was irradiated and injected, Group II was not irradiated but 

 was injected, and Group III was irradiated but was not injected. The 

 frequency of deaths in the three groups during seven 24-hour periods fol- 

 lowing the time of infection is shown in Table I. 



A marked decrease in the resistance of the mice to staphylococcus infec- 

 tion followed irradiation. This is similar to results with X-rays found 



56 



