Comparative Resistance of Strains of Clostridium botulinum to Gamma Rays1

Abstract

AN-ELLIS, A. (Quartermaster Food and Container Institute for the Armed Forces, U. S. Army, Chicago, Ill.) AND ROBERT B. KOCH. Comparative resistance of strains of Clostridiutn botulinunt to gamma rays. Appl. Microbiol. 10:326-330. 1962.-A total of 102 strains of Clostridiun botulinuml (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 10.70+c of the type A strains, 18.6 %/c of the type B strains, and one of three nontoxigenic strains. Overall , 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 MIrad, and the most sensitive strain studied, ;1B, 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). ClostridiumI botulinumn appears to be the spore-forming food spoilage bacterium most resistant to ionizing radiation (Miorgan and Bohrer, 1953; Morgan and Reed, 1954). Since this organism is toxigenic, the acquiring of information on its radiation tolerance is important, for it must be completely destroyed if radiation is to be used for food preservation. The resistance of selected strains has been studied by several investigators. Denny et al. (1958), Pratt et al. (1958), and Schmidt and Nank (1960) determined the radiation dose necessary to sterilize different foods containing mixed cultures of C. botulinum. Morgan

Radiation Resistance of Spores of Clostridium Species In Aqueous Suspension

“…sporogenes, generally the strain referred to as PA 3679, has been published (e.g. Morgan and Reed, 1954 ;Schmidt and Nank, 1960;Schmidt et al, 1962;Denny et al, 1959 ;Pratt et al, 1959;Anellis and Koch, 1962;Kempe et al, 1957). Cl.…”

Biophysical Aspects of Clostridia

“…perfringens had an intermediate radiation resistance when compared with Cl. botulinum types A and B (Morgan & Bohrer, 1953;Anellis & Koch, 1962).…”

“…The first wide spectrum systematic study with 102 strains of spores of Cl. botulinum types A and B was conducted in the United States Army Laboratories by Anellis & Koch (1962). Unfortunately, quantitative data were developed for only 10 strains of Cl.…”

“…The D,, values were derived from references indicated below either directly or by calculation from survival curves or from D,, doses by setting D,, = 2.303 D8,. The media in which the organisms were irradiated were as follows: cultures 1-11, in phosphate buffer (Anellis & Koch, 1962); 12-15 in pureed peas (Morgan & Rohrer, 1953); 16 in phosphate buffer (Whitehair, 1964); 17 in phosphate buffer (Duggan et al, 1963); 18 in the dry state (Christensen, 1964); 19-20 in phosphate buffer (Bellamy et al, 1955); 21-23 in saline plus 0.5% gelatin (Lawrence et aZ., 1953 I n this connection, it may be advisable not to rush into premature conclusions concerning the relative radiation resistance of strains of C1. botulinum type E. A systematic screening of a significant number of representative strains of type E for their radiation resistance is long overdue.…”

“…This D,, value overlaps with the radiation resistance of the relatively sensitive strain 51 of GI. botulinum type B for which Anellis & Koch (1962) have given a D,, value of 0-129 Mrad. Among the nonclostridial and nonspore forms only a few examples are found of organisms possessing an equally high radiation resistance.…”