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Appl Environ Microbiol. 1962 July; 10(4): 326-330

Comparative Resistance of Strains of Clostridium botulinum to Gamma Rays¹

Quartermaster Food and Container Institute for the Armed Forces, Quartermaster Research and Engineering Command, U.S. Army, Chicago, Illinois

ABSTRACT

A total of 102 strains of Clostridium botulinum (56 strains of type A, 43 type B, and 3 nontoxigenic strains which could not be typed) was examined for resistance to gamma rays. When these organisms were suspended in neutral phosphate buffer in concentrations of 10⁴ spores per tube, the threshold sterilizing dose appeared to be 1.4 Mrad. Partial survival to 1.4 Mrad was shown by 10.7% of the type A strains, 18.6% of the type B strains, and one of three nontoxigenic strains. Over-all, type A strains indicated higher radioresistance than type B strains, although there was overlapping. Representatives of the most resistant strains had D values of 0.317 to 0.336 Mrad; the D values of an intermediate group were 0.224 to 0.253 Mrad, and the most sensitive strain studied, 51B, had a D value of 0.129 Mrad. The radioresistance of Putrefactive Anaerobe 3679, strain S-2, was comparable to the intermediate C. botulinum group (D = 0.209).

² Present address: Minneapolis Honeywell Regulator Co., Honeywell Research Center, Hopkins, Minn.

¹ A preliminary account of this work was presented at the 62nd Annual Meeting of the American Society for Microbiology (Bacteriol. Proc., p. 30, 1962).