Endogenous Infection in Mice Irradiated with Fast Neutrons or Gamma Rays. ∗

Abstract

Summary

1. Single, 90-minute irradiation with fast neutrons within the lethal range (175-250 rep) resulted in early deaths among CF No. 1 female mice with a significant peak in the mortality curve 4-8 days after exposure. Among 129 neutron-irradiated mice (216-265 rep: LD_60-98—30 days), sacrificed for bacteriological examination, positive cultures of heart's blood and/or spleen were first obtained on the 4th day, and coincided with the onset of mortality. Between the 4th and 8th days after exposure, approximately 40% of the sacrificed mice showed positive cultures. 2. After comparable irradiation with gamma rays (Co⁶⁰), from 750-1300 r, deaths occurred later, with a peak approximately 12-14 days post-exposure. Gamma-irradiated mice (900-940 r) were found to have positive blood and/or spleen cultures during the latter part of the second week. There seems to be a close correlation between bacteremia and time of death following these 2 ionizing radiations. 3. All the microorganisms recovered in cultures were found to be members of the normal enteric flora of the mouse. 4. The bacteremia, as measured by colony counts on heart's blood was less severe in the neutron-irradiated than in the γ-irradiated mice.