Effects of Pseudomonas contamination or antibiotic decontamination of the GI tract on acute radiation lethality

The influence of antibiotic decontamination or Psuedomonas contamination of the GI tract prior to whole-body neutron or gamma irradiation was studied. For neutron doses greater than 6.7 Gy and gamma ray doses greater than 14.4 Gy, the median survival time of SPF rats was relatively constant at 4.4 days, indicating death was due to intestinal injury. Within the dose range of 4.9 to 6.7 Gy of neutrons or 9.6 to 14.4 Gy of photons, median survival time was inversely related to dose and varied from 12 to 4.6 days. Decontamination or Pseudomonas contamination of the GI tract increased or decreased, respectively, median survival time 1 to 5 days in this survival dose dependent range. The effects of these treatments, however, were negligible in the range of doses in which median survival time was dose independent. These treatments had little effect on the ultimate survival after irradiation as measured by either the LD50/5 day or LD50/30 day endpoints