MODIFICATION OF ANTHRAX BY IONIZING RADIATION
Since dogs are not susceptible to anthrax when inoculated cutaneously, the possible effect of irradiation on susceptibility was explored. Beagles received x irradiation combined with anthrax either simultaneously or three days after irradiation. The controls were irradiated or infected with anthrax alone. A single dose of 125, 250, or 325 r total-body 1-Mev x irradiation was used, which was either equall to or less than the LD/sub 50/ for dogs. A dose rate of 68 r/min in air was used. The distal 1/3 of the femur and the tibia of both hind legs of some dogs in the 250-r group were shielded from radiation. Spores of Bacillus anthracis which had been heat-shocked 48 hr earlier were injected in two doses (5 x 10/sup 4/ or 1 x 10/sup 6/ spores) by the subcutaneous route into the right axilla either simultaneously with or three days after irradiation. Regardless of dose, anthrax alone did not kill dogs. Irradiation alone killed three of six animals in the 250-r group, two of two in the 325-r group, and none in the 125-r group. The dogs died with the acute radiation syndrome characterized by severe lymphohematopoietic depletion and multiple visceral hemorrhages or manifestations of a hemorrhage diathesis. Lymphopenia was observed. Shielding of hind legs protected the irradiated animals from death. Anthrax combined with irradiation killed most of the dogs, inoculated with either high or low doses of anthrax, between 6 and 12 days after infection regardless of dose and time of irradiation. Shielding of the hind legs of irradiated anthrax- infected dogs did not fully protect the dogs from death; four of seven animals in this group died. In contradistinction to the controls, irradiated anthrax- infected dogs invariably developed septicemia with concomitant diffuse and massive cellulitis and a peculiar histopathologic reaction. The histopathologic reaction was essentially hemorrhagic, poor in inflammatory cells, and exceptionally rich in bacilli and bacterial thrombi. This reaction was not observed in other species injected with anthrax. Thus, the normal resistance of the dog to anthrax was markedly reduced by irradiation. Irradiation may increase the harmful effect of anthrax by disturbing the mechanism of defense in this resistant host. This is probably due to damage to the lymphatic and hematopoietic systems by irradiation, further complicated by the infection. Therefore, this combination seems to create a favorable medium for anthrax spores to germinate and multiply. It seemed to stimulate the germination with rapid dissemination and overwhelming septicemia. This was confirmed by the fact that no bacteremia nor significant, persistent cellulitis was observed in the dogs infected with anthrax alone, while irradiated anthrax-infected dogs died with massive, overwhelming septicemia and extensive cellulitis. (BBB)
- Research Organization:
- Fort Detrick, Frederick, Md.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-015858
- OSTI ID:
- 4061237
- Journal Information:
- J. Infect. Diseases, Vol. Vol: 113; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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