Growth temperature-induced changes in resistance of Listeria monocytogenes and Yersinia enterocolitica to X-ray irradiation.

This study aimed to evaluate the effect of different growth temperatures on the resistance of Listeria monocytogenes and Yersinia enterocolitica to low-energy X-ray irradiation and elucidate the mechanisms of resistance variability. The X-ray treatment at a dose of 1.0 kGy resulted in 4.00-, 4.87-, 3.98-, and 2.27-log reductions in cell counts of L. monocytogenes cultured at 37, 25, 15, and 4 °C, respectively. Cell counts of Y. enterocolitica , cultured at 37, 25, 15, and 4 °C, in phosphate-buffered saline decreased by 3.96, 4.98, 3.79, and 3.25 log CFU/mL, respectively, after X-ray irradiation at 0.4 kGy. In addition, the increased resistance to X-rays at low temperatures (4 °C) was induced by different mechanisms in the two pathogens. The results reveal that the key mechanisms for the change in resistance of L. monocytogenes and Y. enterocolitica to X-ray irradiation under different growth temperatures are efflux pump malfunction and DNA damage, respectively. These results suggest that the stress resistance status of L. monocytogenes and Y. enterocolitica cultured at different growth temperatures (37, 25, 15, and 4 °C) should be considered for application in low-dose X-ray irradiation in the food industry. • Growth temperature influenced the resistance of L. monocytogenes and Y. enterocolitica to X-ray irradiation. • The resistance of the pathogens to X-ray irradiation was the highest in cells cultured at 4 °C. • Efflux pump malfunction may be the main mechanism underlying the change in X-ray resistance of L. monocytogenes. • DNA damage may be the main mechanism underlying the change in X-ray resistance Y. enterocolitica. [ABSTRACT FROM AUTHOR]