Effect of environmental stresses on the sensitivity of Enterobacter sakazakii in powdered infant milk formula to gamma radiation

Aim: To evaluate the effect of starvation, heat, cold, acid, alkaline, chlorine and ethanol stresses on the resistance of Enterobacter sakazakii in powdered infant milk formula (PIMF) towards gamma radiation. Methods and Results: Stressed cells of E. sakazakii ATCC 51329 and four other food isolate strains were mixed individually with PIMF, kept overnight at room temperature, and then exposed to gamma radiation up to 7.5 kGy. The D₁₀-values were determined using linear regression and for the stressed E. sakazakii strains these values ranged from 0.82 to 1.95 kGy. Conclusions: Environmental stresses did not significantly change the sensitivity of most E. sakazakii strains to ionizing radiation. Significance and Impact of the Study: Data obtained established that most forms of environmental stress are unlikely to significantly enhance the resistance of E. sakazakii strains to lethal, low dose irradiation treatment.