STUDIES ON THE IRRADIATION OF MICROORGANISMS IN RELATION TO FOOD PRESERVATION: I. THE COMPARATIVE SENSITIVITIES OF SPECIFIC BACTERIA OF PUBLIC HEALTH SIGNIFICANCE

Abstract

The limits of tolerance to gamma irradiation have been determined for 21 cultures representative of the following bacterial species of public health significance in foods: Staphylococcus aureus, Escherichia coli (types I and II), Aerobacler aerogenes, A. cloacae, Streptococcus faecalis, Salmonella gallinarum, S. tennessee, Mycobacterium tuberculosis, Clostridium botulinum (types A and E). A several-fold difference in radiation sensitivity has been demonstrated, specific sensitivity being influenced by the nature of the suspending medium during irradiation.Spores of C. botulinum, type A, were more resistant than those of type E, while six strains of staphylococci of differing phage pattern showed closely similar tolerances. The most sensitive species among those tested was M. tuberculosis. The coliform organisms were more sensitive than the salmonellae, which, in turn, were more sensitive than the staphylococci and S. faecalis. Destruction of coliform bacteria in irradiated foods cannot, therefore, be used as an index of adequate pasteurization.Staphylococcal emetic toxin present in pork sausage and suspended in culture filtrates was destroyed by irradiation at comparatively low levels in contradistinction to the findings for the toxin of C. botulinum.