Effects of sporulation media and strain on thermal resistance of Bacillus cereus spores

Summary Spores of Bacillus cereus strains ATCC 7004, ATCC 4342 and ATCC 9818 were produced in four sporulation media (Nutrient Agar supplemented with 1 ppm Mn2+, Fortified Nutrient Agar, Angelotti Medium and Milk Agar) and their percentages of sporulation and heat resistance parameters obtained in a wide temperature range were compared. In all conditions studied, high rates of sporulation were obtained. Clear differences among D-values for spores produced in the four media were observed. the medium which yielded the most resistant spores and the magnitude with which the sporulation medium affected D-values was different for each strain. z-Values of the three strains were not influenced by the medium used to obtain spores.